TY - JOUR T1 - Guanine content of microRNAs is associated with their tumor suppressive and oncogenic roles in lung and breast cancers JF - bioRxiv DO - 10.1101/518472 SP - 518472 AU - Amit Cohen AU - Mario Alberto Burgos-Aceves AU - Yoav Smith Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/01/11/518472.abstract N2 - Background microRNAs (miRNAs, miRs) are small noncoding RNAs that negatively regulate gene expression at the post-transcriptional level and fine-tune gene functions. A global repression in miRNAs expression in different types of human tumors, after exposure to cigarette-smoke, or to the hormone estrogen, was shown to be associated with guanine (G) enrichment in the terminal loops (TLs) of their precursors.Methods we integrated the G content of miRNA mature forms and precursor miRNA terminal loops with their described function in the literature, as indicated by PubMed database. Gene Ontology term analysis described the pathways in which the G enriched miRNA targets are involved.Results we show here an association between the relative G enrichment of precursor miRNAs TLs and their tendency to act as tumor suppressive miRs in human lung and breast cancers. Another association was observed between the high G content of the miRNAs 5-mature forms and their tendency to act as oncomiRs.Conclusions the results support previous findings suggesting that the G sequence content is an important feature determining miRNAs expression and function, and open the way for future cancer investigations in this direction.ContributionsConception and design: ACAdministrative support: MAB-AProvision of study materials or patients: AC, MAB-ACollection and assembly of data: All authorsData analysis and interpretation: AC, YSManuscript writing: All authorsFinal approval of manuscript: All authors. ER -