The biochemical characterization of identified tRNA ligase enzymes revealed that they accept not only tRNA exon halves but also a broad range of artificial substrates such as nucleolytic RNA fragments, synthetic RNA duplexes, and linear introns generated by tRNA endonucleases [52, 53, 55, 97, [102] [103] [104] [105] . In addition, human cell extracts have been shown to not only ligate 2 0 ,3 0cyclic phosphate bearing but also 3 0 -phosphate-terminated RNA substrates [97, 138] . Biochemical fractionation of HeLa extracts revealed that RNA 3 0 -phosphate terminal cyclase RTCD1 can convert RNA 3 0 -phosphates into 2 0 ,3 0 -cyclic phosphates in an ATP-dependent reaction [139, 140] . Despite the thorough characterization of bacterial and human RNA 3 0 -phosphate terminal cyclase proteins [140, 141] , the physiological function of this enzyme class is still unknown. The recent mechanistic characterization of RtcB from E. coli suggests that 3 0 -phosphate-terminated RNA is per se a substrate for this enzyme [108] , raising questions about the genuine function of RNA terminal cyclase RtcA in E. coli. The potential to prepare a variety of RNA termini for ligation and the relaxed substrate specificity of the ligase itself in many organisms suggests that tRNA splicing enzymes might also act in other biological contexts. As an example of such a case, ScTRL1 has been shown to be involved in stress-induced, non-canonical splicing of the HAC1 transcript in S. cerevisiae [142, 143] . A related pathway acts in human cells, however, the involved RNA ligase has to date not been identified [144] [145] [146] [147] . Furthermore, RNA ligases have been proposed as host factors for the propagation of viruses, viroids, and viroidlike satellite RNAs in humans and plants [148] . In fact, HSPC117 and DDX1 are involved in RNA processing during replication of the hepatitis delta virus [121] , presumably acting as the host RNA ligase factors assumed to be required for cyclization of the viral RNA genome as previously proposed [149] . Furthermore, components of the HSPC117-complex together with the RNA cyclase, RTCD1, have been shown to interact with kinesin-associated RNA transport granules in mouse brain extracts [150] . The exact functions of these RNA metabolic enzymes in the context of RNA transport await further experiments. In addition to processing of RNA transcripts of various origins, RNA ligases are assumed to be involved in RNA repair pathways. Apart from the wellstudied example of tRNA repair by bacteriophage T4 RNA ligase [62] , further examples of RNA repair have been revealed [67, 79, 151] . These studies showed an amazing potential of RNA ligases to function as safeguards against the deleterious effects of cytotoxic nucleases in yeast and bacteria. Similar efforts might unveil examples of RNA repair in unanticipated physiological contexts not only in bacteria and yeast but also in higher organisms. The high degree of conservation of HSPC117/RtcB proteins and preliminary data indicating that HSPC117 seems to be encoded by an essential gene in mice [152] are highly suggestive of universal and important roles for this protein family. Assigning a biological function to the operon harboring the ligase, rtcB, and the cyclase, rtcA, in some bacteria may help to uncover functions of this type of ligase unrelated to tRNA splicing since E. coli does not encode for intron harboring tRNAs. Finally, the identification of genuine substrates interacting with RNA ligase proteins in vivo may yield fascinating insights into the various processes potentially requiring RNA ligases. Diversity and roles of (t)RNA ligases 2667 ESP Abstracts 2012  OFP-01-002 Intraoperative evaluation of breast cancer sentinel lymph node metastasis with an automated molecular detection method as an alternative to standard pathological evaluation F. Beca * , E. Rios, P. Pontes, I. Amendoeira * Centro Hospitalar de São João, Anatomic Pathology, Porto, Portugal Objective: One-step nucleic acid amplification assay (OSNA) from Sysmex® is an automated system to detect sentinel lymph node (SLN) metastasis in breast cancer patients. This assay is based on the detection of cytokeratin 19 mRNA amplification by reverse-transcription loop-mediated isothermal amplification. Traditionally intraoperative evaluation of SLN is accomplished by cytology and/or frozen section, accounting for heavy workload to pathology department. The objective of this study is to compare the OSNA assay with our standard processing for intraoperative SLN evaluation. Method: 82 SLN from 45 patients with CK19+ and invasive primary carcinomas where simultaneously evaluated by cytology and/or frozen section and by OSNA assay. Results where compared with gold-standard definitive H&E evaluation (serially sectioned at 150 μm intervals). Results: The sensitivity and specificity of OSNA assay was 92.3 % and 98.2 %, respectively with a positive predictive value (PPV) and a negative predictive value (NPV) of 96 %. For standard intraoperative evaluation, specificity was 100 % and sensitivity was 73.0 %. Conclusion: OSNA assay showed similar specificity and higher sensitivity than standard pathologic examination. These findings suggest it can be used as an accurate tool for intraoperative evaluation of SLNs metastasis and possibly contribute to reducing the need for re-intervention for axillary lymph node dissection. Objective: Antracycline-based chemotherapy represents a standard of care in breast cancer patients especially who overexpress HER-2. Topoisomerase 2A has been considered a molecular target for antracyclines and its co-amplification with HER-2 genes has been proposed. In our study we investigated if Topoisomerase 2A overexpression can be used as a molecular marker on predicting response to antracycline-based chemotherapy.