7sksmall nuclear RNA transcription level downregulates in human breast cancer cells and tissue

The small nuclear non-coding RNA (snRNA) 7SK is an abundant RNA of 331 nucleotides in animals, which is transcribed by RNA polymerase III (Pol III) .It is shown that regulating the activity of the Positive Transcriptional Elongation Factor b (P-TEFb) is the key function of 7SK. Eilebrecht, S., et al.shown that 7SK RNA has a regulatory role on HMGA1, involved in neoplastic transformation and tumor progression activity. Recently we have discovered that 7SK snRNA over-expression reduces human embryonic kidney (HEK) 293T cancer cell line viability. Based upon these data we proposed that 7SK transcription level might be changed in cancerous cells and tissues compared to normal. MCF-10 and MDA-MB-231 cell lines was cultured and breast cancer and normal tissue samples were gift from tissue bank of Stem Cell Technology Research Center. Total RNA was isolated from cells and tissues. Firststrand cDNA was synthesized and quantitative real-time PCR was performed for 7SK snRNA and Gapdh primers. 7sk down-regulation was observed in metastatic breast cancer cell line MDA-MB-231 in comparisonwith normal breast epithelial celllineMCF10.Also 7sk down-regulation was observed in cancer breast tissues in comparison with normal breast tissues. In this regards, overexpression of the 7SK could be a powerful tool for blocking cancer progression by controlling the activity of P-TEFb. Our data reveals that 7SK transcription is significantly reduced in human breast cancers cells and tissues relative to normal cells and tissues supporting hypothesis that 7SK has anti-proliferative and tumor-suppressing functions.