BACKGROUND
members of the s <dig> protein family comprise a multigenic group of non-ubiquitous cytoplasmic ca2+-binding proteins of the ef-hand type, differentially expressed in a wide variety of cell types.
in particular, s100a <dig> and s100a <dig> also known as calgranulins are abundant in myeloid cells.
the expression of s100a <dig> and s100a <dig> is increased in various disorders, such as rheumatoid arthritis, inflammatory bowel disease and vasculitis  <cit> .
the s100/calgranulins are associated with inflammatory disorders as they are secreted from phagocytes upon cellular activation  <cit> , and track disease activity.
in addition to their abundance in myeloid cells, s100a <dig> and s100a <dig> can also be found in the epidermis as a response to stress.
for example, they are significantly up-regulated in differentiating suprabasal wound keratinocytes  <cit> , in response to uvb irradiation  <cit> , and in psoriasis keratinocytes  <cit> , suggesting a role for these proteins in the pathogenesis of certain diseases.
based on these findings, the two s <dig> proteins have been referred to as stress-regulated proteins  <cit> .
an additional important indication for their involvement in inflammatory and neoplastic disorders is that most s <dig> genes are found near a region on human chromosome 1q <dig> which is responsible for a number of chromosomal abnormalities  <cit> .
this results in a dysregulated expression of s100a <dig> as well as other s <dig> genes associated with neoplasias  <cit> .
although the function of s <dig> proteins in cancer cells in most cases is still unknown, the specific expression patterns of these proteins is a valuable prognostic tool.
in addition, a psoriasis susceptibility region, the psors <dig> locus, is mapped to chromosome 1q <dig>  <cit> .
despite a number of distinct regulatory regions located upstream of the transcription initiation site that are known to either activate or repress promoter activity of s <dig> genes in a differentiation and tissue/cell-specific manner, the corresponding nuclear factors as well as the underlying molecular mechanisms still remain unclear  <cit> .
in addition to pu.
<dig>  <cit> , c/ebp-α and -β  <cit>  have been shown to drive s100a <dig> gene expression in the myeloid lineage.
recently, cytokine oncostatin m  has been demonstrated to strongly induce the s100a <dig> gene expression  <cit> .
promoter analysis provided evidence that s100a <dig> represents a novel om-regulated gene acting through the stat3-signaling cascade.
this finding is in accordance with another study showing that il- <dig> up-regulates the expression of s100a <dig>  s100a <dig>  and s100a <dig> in keratinocytes since il- <dig> induces stat <dig> activation in keratinocytes  <cit> .
in a previous study, we identified a regulatory element within the s100a <dig> promoter referred to as mrp regulatory element  that drives the s100a <dig> gene expression in a cell-specific and differentiation-dependent manner  <cit> .
this regulatory region is located at position - <dig> to - <dig> bp, and two distinct nuclear complexes were demonstrated to bind to this region.
interestingly, the formation of the nuclear protein complexes closely correlates with the myeloid-specific expression of the s100a <dig> gene and, were therefore referred to as mre-binding complex a  and mbcb, respectively.
analysis of one of the two nuclear complexes revealed a heterocomplex consisting of transcriptional intermediary factor 1β  and a yet unidentified protein with homology to krab domain-containing  zinc finger proteins   <cit> .
in order to identify the other nuclear complex we performed dna affinity chromatography studies employing mre oligonucleotides as an affinity matrix.
further extensive investigations provide strong evidence that a complex of parp- <dig>  ku <dig> and ku <dig> was involved in the regulation of the s100a <dig> gene expression.
this finding was confirmed by chromatin immunoprecipitation  analysis.
RESULTS
identification of mre-binding proteins
in order to identify the proteins participating in the formation of the complex we performed dna affinity chromatography.
nuclear extracts of raji cells were subjected to affinity purification employing mre oligonucleotides as an affinity matrix.
nuclear proteins bound to mre were eluted in a stepwise gradient with  <dig>   <dig>  and  <dig>  mm nacl and then analyzed by emsa.
only the proteins of the  <dig> m nacl eluate displayed dna-binding activity, indicating that they specifically interacted with the probe .
the binding of proteins to mre was specific, as an excess of non-labeled mre oligonucleotide efficiently competed with the labeled probe in complex formation, whereas the mutant oligonucleotide mre  did not compete .
our previous study showed that this mre mutant oligonucleotide was unable to compete for binding to mre oligonucleotide  <cit> .
then the proteins of the  <dig> m nacl eluate were precipitated using the uppa concentrate kit, then subjected to sds-page, and finally visualized by coomassie staining .
seven protein bands with apparent molecular weights of  <dig>   <dig>   <dig>   <dig>   <dig>  and 25-kda were detected.
the protein bands were excised from the gel, digested with trypsin, and subjected to maldi-ms for peptide mass fingerprint and to esi-ms/ms for peptide sequencing.
the data obtained were analyzed using swissprot and ncbi databases.
the identified proteins are summarized in table  <dig>
specifically, parp- <dig>  was identified in band  <dig> by peptide mass fingerprint and peptide sequencing .
fragments of parp- <dig> were found in nearly all bands, especially in band  <dig> .
ku <dig>  was identified in band  <dig>  and ku <dig>  in band  <dig> by peptide mass fingerprint and peptide sequencing .
the identity of parp- <dig> and ku <dig> was also confirmed by western blotting .
parp- <dig> represents a nuclear enzyme with a dna nick sensor function  <cit> .
upon binding to broken dna, parp becomes activated and cleaves nad+ into nicotinamide and adp-ribose.
it then polymerizes adp-ribose on nuclear acceptor proteins including histones, transcription factors, and parp itself  <cit> .
poly adp-ribosylation has been implicated in a number of cellular processes, such as dna repair  <cit> , transcriptional regulation  <cit> , and cell cycle progression  <cit> .
excessive parp activation induced by oxidative stress has been shown to decrease cellular nad+ and atp pools, resulting in cell dysfunction or necrotic cell death  <cit> .
the parp activation pathway contributes to tissue injury in various forms of shock, inflammation, trauma, and reperfusion injury, as indicated by the protection provided by parp inhibitors or the parp-/- phenotype in these disease models  <cit> .
both ku <dig> and ku <dig> form the heterodimeric dna binding complex ku that was originally identified two decades ago as a major target of autoantibodies in japanese patients with the scleroderma-polymyositis overlap syndrome  <cit> .
the autoantibodies against ku have since been found in subsets of patients suffering from a number of different autoimmune diseases, including systemic lupus erythematosus and scleroderma.
ku is best known for its crucial role in dna repair  <cit> .
ku is involved in both major pathways of dna double strand break repair: homologous recombination and non-homologous end joining.
besides its vital role in dna repair, reports have implicated ku in certain other cellular processes, including telomere maintenance, antigen receptor gene arrangements, cell cycle regulation, regulation of heat shock-induced responses, and specific gene transcription and apoptosis.
for example, it has been shown that ku is required for interleukin-13/-4-induction of 15-lipoxygenase- <dig> gene expression in human epithelial cells  <cit> .
here, ku is induced in response to il- <dig> and il- <dig>  and a  <dig> bp region within the - <dig> to - <dig> bp region of the 15-lo- <dig> promoter is required for its binding and subsequent induction of 15-lo- <dig> gene expression.
studies with cells and/or animals deficient in ku have shown that dysfunction and dysregulation of the above-mentioned processes lead to tumor development  <cit> .
in addition, a rare microsatellite polymorphism in the ku <dig> gene is associated with cancer in patients with varying radiosensitivity  <cit> .
since parp- <dig> and ku bind to dna double strand breaks we performed dna affinity chromatography employing the mre mutant oligonucleotide mre  as affinity matrix in order to verify whether this binding is specific to the mre sequence.
our previous study showed that this mre mutant oligonucleotide was unable to compete for binding to mre oligonucleotide  <cit> .
we failed to detect dna-binding activity in the corresponding  <dig> m nacl eluate, and after protein precipitation, no protein bands were visualized by coomassie staining , indicating that the high affinity of parp- <dig> and ku to dna double strand breaks was not responsible for their binding to the mre oligonucleotide.
chip experiment
to verify whether parp- <dig> and ku <dig> can directly bind to the s100a <dig> promoter in vivo, we performed chromatin immunoprecipitation.
cross-linked chromatin from raji cells was immunoprecipitated with specific antibodies against parp- <dig>  ku <dig>  and the nonspecific antibodies igg.
after pcr analysis using s100a <dig> promoter-specific oligonucleotides, we found that parp- <dig> and ku <dig> specifically bind the regulatory region of s100a <dig> promoter.
chromatin immunoprecipitates with nonspecific igg antibodies did not reveal any specific binding to the analyzed regulatory regions .
thus, the chip experiments clearly confirmed that both parp- <dig> and ku <dig> specifically bind to mre.
it is likely that parp- <dig> and ku <dig>  are components of the nuclear complex that binds to mre.
this assumption is supported by several reports demonstrating the interaction of parp- <dig> with ku proteins.
a complex formed by parp- <dig>  ku proteins and c/ebpα has been shown to be involved in the increasing sensitivity of prostate cancer cells to dna damage  <cit> .
strong evidence that parp- <dig> is involved in s100a <dig> gene regulation has also recently reported by martin-oliva and co-workers  <cit> .
they showed that tpa-induced s100a <dig> gene expression was blocked after the pharmacologic inhibition of parp- <dig> with  <dig> -dihydro-5- -1-isoquinolinone.
in accordance with this finding, they also did not observe tpa-induced s100a <dig> gene expression in parp <dig> knockout mice.
therefore, we investigated s100a <dig> gene expression in hacat keratinocytes in the absence and presence of the parp- <dig> inhibitor  <dig> -isoquinolinediol .
both tpa- and tnfα- stimulation resulted in increased levels of s100a <dig> mrna transcripts.
s100a <dig> gene expression was n <dig> =  <dig> -fold increased after tpa treatment and n <dig> =  <dig> -fold increased after tnfα stimulation, respectively .
while the tpa-increased s100a <dig> gene expression was completely abrrogated by diq, tnfα-induced s100a <dig> gene expression was not affected by diq.
together with the report of martin-oliva and co-workers  <cit> , these findings indicate the involvement of parp- <dig> in s100a <dig> gene regulation.
further correlations of parp- <dig> and s100a <dig> gene expression are found in other reports: dazard and co-workers  <cit>  reported that in addition to other genes, s100a <dig> gene expression is up-regulated in normal human epidermal keratinocytes in response to ultraviolet b radiation .
induction of s100a <dig> gene expression is also found in epithelial cells in specific pathophysiological conditions, such as wound healing  <cit>  and psoriasis  <cit> .
similarly, parp- <dig> activity is increased after uv irradiation and in psoriasis  <cit> .
our finding that parp- <dig> regulates the s100a <dig> gene expression represents the first link between this nuclear protein and the s <dig> protein family.
what is the molecular mechanism by which parp- <dig> regulates s100a <dig> gene expression?
roles for parp- <dig> in the transcriptional regulation of specific genes have been demonstrated in several physiological contexts  <cit> .
from these studies, at least two different mechanisms have been proposed for the regulation of transcription by parp-1:  modulating chromatin structure, and  acting as part of gene-specific enhancer/promoter-binding complexes.
as a component of enhancer/promoter-binding complexes, parp- <dig> acts to stimulate transcription with some activators, while inhibiting transcription with others, depending on the cell type and promoter context.
in some cases, parp- <dig> enzymatic activity is not required for its transcriptional co-regulator function .
recently, ju and co-workers  <cit>  have presented some mechanistic details of how parp- <dig> acts as a modulator of the chromatin structure: in complex with dna topoisomerase iiβ , parp- <dig> is recruited to specific promoter regions.
then, transient dsdna break formation mediated by topoiiβ induces parp- <dig> enzymatic activity, which is required for a nucleosome-specific histone h1-high-mobility group b exchange event and for local changes of chromatin architecture.
the authors conclude that topoiiβ/parp- <dig> complex-mediated transient dsdna breaks serve as a general mechanism for regulated initiation of gene transcription by nuclear receptors and other classes of dna binding transcription factors, including ap- <dig>
ap- <dig> has been assumed to be involved in s100a <dig> gene expression  <cit> , and polyation of ap- <dig> by parp- <dig> appears to be important for its binding activity as shown by martin-oliva and co-workers  <cit> .
pharmacological inhibition of parp- <dig> results in significant reduction of the relative levels of ap-1-binding activity compared to mice treated with tpa  <cit> .
in contrast, nf-κb activation was not reduced by parp- <dig> inhibitors but reduced in parp-1-/- cells  <cit> .
it has been reported that in addition to nf-κb, ap- <dig> is also induced by tnfα receptor ligation  <cit> .
in the present study, however, we demonstrated that tpa-increased s100a <dig> gene expression was blocked by the parp- <dig> inhibitor, while tnfα-increased s100a <dig> mrna level was not affected.
these findings might indicate that both interaction of parp- <dig> with transcription factors and parp- <dig> mediated polyation are important for s100a <dig> gene expression.
it is noteworthy to point to the association of s <dig> proteins with tumorgenesis.
an increasing body of evidence provided by several reports shows that s <dig> gene are differentially regulated in various cancer cells  <cit> .
parp- <dig> and ku have also been assigned a role in tumorgenesis.
therefore, this study provides first insights into the molecular mechanism of s100a <dig> gene regulation, and it opens an avenue for a better understanding as to why s <dig> gene expression is associated with tumor promotion.
nevertheless, we are aware that the exact elucidation of the dna/protein complexes will require further intensive investigations.
CONCLUSIONS
the observations reported here demonstrate the role of parp- <dig>  in s100a <dig> gene regulation.
the association of s <dig> proteins with inflammatory and neoplastic disorders together with the role of parp- <dig> in stress response and tumorgenesis might indicate the link between s <dig> and inflammation-associated cancer.

 members of the s protein family comprise a multigenic group of non-ubiquitous cytoplasmic ca2+-binding proteins of the ef-hand type, differentially expressed in a wide variety of cell types. in particular, s100a and s100a also known as calgranulins are abundant in myeloid cells. the expression of s100a and s100a is increased in various disorders, such as rheumatoid arthritis, inflammatory bowel disease and vasculitis. the s100/calgranulins are associated with inflammatory disorders as they are secreted from phagocytes upon cellular activation, and track disease activity. in addition to their abundance in myeloid cells, s100a and s100a can also be found in the epidermis as a response to stress. for example, they are significantly up-regulated in differentiating suprabasal wound keratinocytes, in response to uvb irradiation, and in psoriasis keratinocytes, suggesting a role for these proteins in the pathogenesis of certain diseases. based on these findings, the two s proteins have been referred to as stress-regulated proteins. an additional important indication for their involvement in inflammatory and neoplastic disorders is that most s genes are found near a region on human chromosome 1q which is responsible for a number of chromosomal abnormalities. this results in a dysregulated expression of s100a as well as other s genes associated with neoplasias. although the function of s proteins in cancer cells in most cases is still unknown, the specific expression patterns of these proteins is a valuable prognostic tool. in addition, a psoriasis susceptibility region, the psors locus, is mapped to chromosome 1q. despite a number of distinct regulatory regions located upstream of the transcription initiation site that are known to either activate or repress promoter activity of s genes in a differentiation and tissue/cell-specific manner, the corresponding nuclear factors as well as the underlying molecular mechanisms still remain unclear. in addition to pu., c/ebp-α and -β have been shown to drive s100a gene expression in the myeloid lineage. recently, cytokine oncostatin m has been demonstrated to strongly induce the s100a gene expression. promoter analysis provided evidence that s100a represents a novel om-regulated gene acting through the stat3-signaling cascade. this finding is in accordance with another study showing that il- up-regulates the expression of s100a s100a and s100a in keratinocytes since il- induces stat activation in keratinocytes. in a previous study, we identified a regulatory element within the s100a promoter referred to as mrp regulatory element that drives the s100a gene expression in a cell-specific and differentiation-dependent manner. this regulatory region is located at position - to - bp, and two distinct nuclear complexes were demonstrated to bind to this region. interestingly, the formation of the nuclear protein complexes closely correlates with the myeloid-specific expression of the s100a gene and, were therefore referred to as mre-binding complex a and mbcb, respectively. analysis of one of the two nuclear complexes revealed a heterocomplex consisting of transcriptional intermediary factor 1β and a yet unidentified protein with homology to krab domain-containing zinc finger proteins. in order to identify the other nuclear complex we performed dna affinity chromatography studies employing mre oligonucleotides as an affinity matrix. further extensive investigations provide strong evidence that a complex of parp- ku and ku was involved in the regulation of the s100a gene expression. this finding was confirmed by chromatin immunoprecipitation analysis.  identification of mre-binding proteins in order to identify the proteins participating in the formation of the complex we performed dna affinity chromatography. nuclear extracts of raji cells were subjected to affinity purification employing mre oligonucleotides as an affinity matrix. nuclear proteins bound to mre were eluted in a stepwise gradient with and mm nacl and then analyzed by emsa. only the proteins of the m nacl eluate displayed dna-binding activity, indicating that they specifically interacted with the probe. the binding of proteins to mre was specific, as an excess of non-labeled mre oligonucleotide efficiently competed with the labeled probe in complex formation, whereas the mutant oligonucleotide mre did not compete. our previous study showed that this mre mutant oligonucleotide was unable to compete for binding to mre oligonucleotide. then the proteins of the m nacl eluate were precipitated using the uppa concentrate kit, then subjected to sds-page, and finally visualized by coomassie staining. seven protein bands with apparent molecular weights of and 25-kda were detected. the protein bands were excised from the gel, digested with trypsin, and subjected to maldi-ms for peptide mass fingerprint and to esi-ms/ms for peptide sequencing. the data obtained were analyzed using swissprot and ncbi databases. the identified proteins are summarized in table specifically, parp- was identified in band by peptide mass fingerprint and peptide sequencing. fragments of parp- were found in nearly all bands, especially in band. ku was identified in band and ku in band by peptide mass fingerprint and peptide sequencing. the identity of parp- and ku was also confirmed by western blotting. parp- represents a nuclear enzyme with a dna nick sensor function. upon binding to broken dna, parp becomes activated and cleaves nad+ into nicotinamide and adp-ribose. it then polymerizes adp-ribose on nuclear acceptor proteins including histones, transcription factors, and parp itself. poly adp-ribosylation has been implicated in a number of cellular processes, such as dna repair, transcriptional regulation, and cell cycle progression. excessive parp activation induced by oxidative stress has been shown to decrease cellular nad+ and atp pools, resulting in cell dysfunction or necrotic cell death. the parp activation pathway contributes to tissue injury in various forms of shock, inflammation, trauma, and reperfusion injury, as indicated by the protection provided by parp inhibitors or the parp-/- phenotype in these disease models. both ku and ku form the heterodimeric dna binding complex ku that was originally identified two decades ago as a major target of autoantibodies in japanese patients with the scleroderma-polymyositis overlap syndrome. the autoantibodies against ku have since been found in subsets of patients suffering from a number of different autoimmune diseases, including systemic lupus erythematosus and scleroderma. ku is best known for its crucial role in dna repair. ku is involved in both major pathways of dna double strand break repair: homologous recombination and non-homologous end joining. besides its vital role in dna repair, reports have implicated ku in certain other cellular processes, including telomere maintenance, antigen receptor gene arrangements, cell cycle regulation, regulation of heat shock-induced responses, and specific gene transcription and apoptosis. for example, it has been shown that ku is required for interleukin-13/-4-induction of 15-lipoxygenase- gene expression in human epithelial cells. here, ku is induced in response to il- and il- and a bp region within the - to - bp region of the 15-lo- promoter is required for its binding and subsequent induction of 15-lo- gene expression. studies with cells and/or animals deficient in ku have shown that dysfunction and dysregulation of the above-mentioned processes lead to tumor development. in addition, a rare microsatellite polymorphism in the ku gene is associated with cancer in patients with varying radiosensitivity. since parp- and ku bind to dna double strand breaks we performed dna affinity chromatography employing the mre mutant oligonucleotide mre as affinity matrix in order to verify whether this binding is specific to the mre sequence. our previous study showed that this mre mutant oligonucleotide was unable to compete for binding to mre oligonucleotide. we failed to detect dna-binding activity in the corresponding m nacl eluate, and after protein precipitation, no protein bands were visualized by coomassie staining, indicating that the high affinity of parp- and ku to dna double strand breaks was not responsible for their binding to the mre oligonucleotide. chip experiment to verify whether parp- and ku can directly bind to the s100a promoter in vivo, we performed chromatin immunoprecipitation. cross-linked chromatin from raji cells was immunoprecipitated with specific antibodies against parp- ku and the nonspecific antibodies igg. after pcr analysis using s100a promoter-specific oligonucleotides, we found that parp- and ku specifically bind the regulatory region of s100a promoter. chromatin immunoprecipitates with nonspecific igg antibodies did not reveal any specific binding to the analyzed regulatory regions. thus, the chip experiments clearly confirmed that both parp- and ku specifically bind to mre. it is likely that parp- and ku are components of the nuclear complex that binds to mre. this assumption is supported by several reports demonstrating the interaction of parp- with ku proteins. a complex formed by parp- ku proteins and c/ebpα has been shown to be involved in the increasing sensitivity of prostate cancer cells to dna damage. strong evidence that parp- is involved in s100a gene regulation has also recently reported by martin-oliva and co-workers. they showed that tpa-induced s100a gene expression was blocked after the pharmacologic inhibition of parp- with -dihydro-5- -1-isoquinolinone. in accordance with this finding, they also did not observe tpa-induced s100a gene expression in parp knockout mice. therefore, we investigated s100a gene expression in hacat keratinocytes in the absence and presence of the parp- inhibitor -isoquinolinediol. both tpa- and tnfα- stimulation resulted in increased levels of s100a mrna transcripts. s100a gene expression was n = -fold increased after tpa treatment and n = -fold increased after tnfα stimulation, respectively. while the tpa-increased s100a gene expression was completely abrrogated by diq, tnfα-induced s100a gene expression was not affected by diq. together with the report of martin-oliva and co-workers, these findings indicate the involvement of parp- in s100a gene regulation. further correlations of parp- and s100a gene expression are found in other reports: dazard and co-workers reported that in addition to other genes, s100a gene expression is up-regulated in normal human epidermal keratinocytes in response to ultraviolet b radiation. induction of s100a gene expression is also found in epithelial cells in specific pathophysiological conditions, such as wound healing and psoriasis. similarly, parp- activity is increased after uv irradiation and in psoriasis. our finding that parp- regulates the s100a gene expression represents the first link between this nuclear protein and the s protein family. what is the molecular mechanism by which parp- regulates s100a gene expression? roles for parp- in the transcriptional regulation of specific genes have been demonstrated in several physiological contexts. from these studies, at least two different mechanisms have been proposed for the regulation of transcription by parp-1: modulating chromatin structure, and acting as part of gene-specific enhancer/promoter-binding complexes. as a component of enhancer/promoter-binding complexes, parp- acts to stimulate transcription with some activators, while inhibiting transcription with others, depending on the cell type and promoter context. in some cases, parp- enzymatic activity is not required for its transcriptional co-regulator function. recently, ju and co-workers have presented some mechanistic details of how parp- acts as a modulator of the chromatin structure: in complex with dna topoisomerase iiβ, parp- is recruited to specific promoter regions. then, transient dsdna break formation mediated by topoiiβ induces parp- enzymatic activity, which is required for a nucleosome-specific histone h1-high-mobility group b exchange event and for local changes of chromatin architecture. the authors conclude that topoiiβ/parp- complex-mediated transient dsdna breaks serve as a general mechanism for regulated initiation of gene transcription by nuclear receptors and other classes of dna binding transcription factors, including ap- ap- has been assumed to be involved in s100a gene expression, and polyation of ap- by parp- appears to be important for its binding activity as shown by martin-oliva and co-workers. pharmacological inhibition of parp- results in significant reduction of the relative levels of ap-1-binding activity compared to mice treated with tpa. in contrast, nf-κb activation was not reduced by parp- inhibitors but reduced in parp-1-/- cells. it has been reported that in addition to nf-κb, ap- is also induced by tnfα receptor ligation. in the present study, however, we demonstrated that tpa-increased s100a gene expression was blocked by the parp- inhibitor, while tnfα-increased s100a mrna level was not affected. these findings might indicate that both interaction of parp- with transcription factors and parp- mediated polyation are important for s100a gene expression. it is noteworthy to point to the association of s proteins with tumorgenesis. an increasing body of evidence provided by several reports shows that s gene are differentially regulated in various cancer cells. parp- and ku have also been assigned a role in tumorgenesis. therefore, this study provides first insights into the molecular mechanism of s100a gene regulation, and it opens an avenue for a better understanding as to why s gene expression is associated with tumor promotion. nevertheless, we are aware that the exact elucidation of the dna/protein complexes will require further intensive investigations.  the observations reported here demonstrate the role of parp- in s100a gene regulation. the association of s proteins with inflammatory and neoplastic disorders together with the role of parp- in stress response and tumorgenesis might indicate the link between s and inflammation-associated cancer. 
furthermore, tpa-induced s100a gene expression in hacat keratinocytes was blocked after the pharmacologic inhibition of parp- with -isoquinolinediol. in the present study, we investigated transcription factors that bind to mre. using the mre motif for a pull-down assay, polypolymerase- and the heterodimeric complex ku70/ku were identified by mass spectrometry and confirmed by chromatin immunoprecipitation. s proteins, a multigenic family of non-ubiquitous cytoplasmic ca2+-binding proteins, have been linked to human pathologies in recent years. the candidates, polypolymerase- and the heterodimeric complex ku70/ku are known to participate in inflammatory disorders as well as tumorgenesis. recently, we characterized a regulatory element within the s100a promotor, referred to as mre that drives the s100a gene expression in a cell type-specific, activation- and differentiation-dependent manner j. biol. dysregulated expression of s proteins, including s100a has been reported in the epidermis as a response to stress and in association with neoplastic disorders.
 s proteins, a multigenic family of non-ubiquitous cytoplasmic ca2+-binding proteins, have been linked to human pathologies in recent years. dysregulated expression of s proteins, including s100a has been reported in the epidermis as a response to stress and in association with neoplastic disorders. recently, we characterized a regulatory element within the s100a promotor, referred to as mre that drives the s100a gene expression in a cell type-specific, activation- and differentiation-dependent manner j. biol. chem. 41879–41887).  in the present study, we investigated transcription factors that bind to mre. using the mre motif for a pull-down assay, polypolymerase- and the heterodimeric complex ku70/ku were identified by mass spectrometry and confirmed by chromatin immunoprecipitation. furthermore, tpa-induced s100a gene expression in hacat keratinocytes was blocked after the pharmacologic inhibition of parp- with -isoquinolinediol.  the candidates, polypolymerase- and the heterodimeric complex ku70/ku are known to participate in inflammatory disorders as well as tumorgenesis. the latter may indicate a possible link between s and inflammation-associated cancer. 