Upstream flanking sequences and transcription of SINEs

SINEs, short interspersed repeated DNA elements, undergo amplification thro ugh retroposition and subsequent integration into a new location in the gen ome. Each new SINE insertion will be located in a new chromosomal environme nt, with different flanking sequences. Modulation of transcription by diffe rent flanking sequences may play an important role in determining which SIN E elements are preferentially active in a genome. We evaluated the ability of upstream flanking sequences to regulate the transcription of three diffe rent SINEs (Alu, B2 and ID) by constructing chimeric constructs with known 5' flanking sequences of RNA polymerase III-transcribed genes. Upstream seq uences from the 7SL RNA gene, U6 RNA gene, vault RNA gene, and BC1 gene inc rease transcription of Alu, B2 and BC1 in transient transfections of NIH3T3 , HeLa, Neuro2a and C6 glioma cell lines. The 7SL sequence proved most effi cient in increasing SINE transcription. The 7SL upstream fused to the BC1 R NA gene (an ID element) was used to create a transgenic mouse line. In cont rast to the tissue-specific endogenous BC1 transcription, BC1 transgene tra nscripts were detected in all tissues tested. However, expression was much higher in those tissues that express the endogenous gene, demonstrating bot h transcriptional and post-transcriptional regulation. The BC1 RNA was dete cted in a similar ribonucleoprotein complex in the different tissues. (C) 2 000 Academic Press.