Abstract 542: Regulation of the telomere healing process by the lncRNA TERRA
Authors: Oliva-Rico Diego A. , Gonzalez-Barrios Rodrigo , Fabian-Morales Eunice , Herrera Luis A. 
Published: May 2015

Abstract
Telomere length is regulated by epigenetic marks that modulate, among other things, the expression of the telomerase catalytic subunit. Telomeres and sub-telomeric regions are enriched in histone marks associated to constitutive heterochromatin. The marks before mentioned are essential for the maintenance of telomere integrity and therefore for genomic stability, but there is another kind of regulation that depends on ncRNAs. This is the case of the lncRNA Telomere repeat-containing RNA (TERRA), an element required for telomeric integrity, considered to hinder chromosomal instability where anaphase bridges, sister chromatid fusions and multi-telomeric regions can take place. This instability leads to chromosomal aberrations that could produce a malignant cell lineage, however, in order for this event to take place, a telomere healing process must occur so that the ribonucleoproteic complex of the telomere can be stabilized once more. For this reason it is important to study the role that the lncRNA TERRA plays in telomere stabilization and how its malfunctioning can bring forth an carcinogenic process. The telomeric regions of interest were analyzed using the data base of the University of California in Santa Cruz (UCSC). We chose the short arm of chromosome 5, where telomerase is encoded, and looked for elements associated to promoter regions such as the presence of the nuclear factor CTCF, Polymerase II, histone marks related with promoters (H3K4me3 and H3K4me1), potential transcription start sites (TSS) and sequences with enhancer potential. We worked with two cell lines of the same cell lineage K562 and SC, in order to have a leukemic and a non-transformed cell model. In order to enrich the amount of TERRA after RNA extraction, we synthesized cDNA using both dT primers and telomere repeat-containing oligonucleotides. The cDNA was used to evaluate the total amount of TERRA in both cell lines using the expression of the ncRNAs U6, HOTAIR and H19 as an amplification reference. We demonstrated that the short arm of chromosome 5 does codify for TERRA, and we verified that only the DNA strand that encodes TERRA was transcribed. Furthermore, we confirmed that the predicted TSS was functional. qPCR showed that there are changes in TERRA expression that take place in accordance with population doubling events. This was observed in the analyzed telomeres of both cell lines used. These results could be related with the natural shortening of telomeres that happens in non-transformed cells, but since such a process is absent in leukemic cells, further investigation is required to answer this query.
Citation Format: Diego A. Oliva-Rico, Rodrigo Gonzalez-Barrios, Eunice Fabian-Morales, Luis A. Herrera. Regulation of the telomere healing process by the lncRNA TERRA. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 542. doi:10.1158/1538-7445.AM2014-542