CELL STRESS AND TRANSLATIONAL INHIBITORS TRANSIENTLY INCREASE THE ABUNDANCE OF MAMMALIAN SINE TRANSCRIPTS

The abundance of Alu RNA is transiently increased by heat shock in hum an cell lines, This effect is specific to Alu repeats among Pol III tr anscribed genes, since the abundance of 7SL, 7SK, 5S and U6 RNAs is es sentially unaffected by heat shock, The rapid induction of Alu express ion precedes the heat shock induction of mRNAs for the ubiquitin and H SP 70 heat shock genes, Heat shock mimetics also transiently induce Al u expression indicating that increased Alu expression is a general cel l-stress response, Cycloheximide treatment rapidly and transiently inc reases the abundance of Alu RNA, Again, compared with other genes tran scribed by Pol III, this increase is specific to Alu, However, as dist inguished from the cell stress response, cycloheximide does not induce expression of HSP 70 and ubiquitin mRNAs. Puromycin also increases Al u expression, suggesting that this response is generally caused by tra nslational inhibition, The response of mammalian SINEs to cell stress and translational inhibition is not limited to SINEs which are Alu hom ologues. Heat shock and cycloheximide each transiently induce Pol III directed expression of B1 and B2 RNAs in mouse cells and C-element RNA in rabbit cells, Together, these three species exemplify the known SI NE composition of placental mammals, suggesting that mammalian SINEs a re similarly regulated and may serve a common function.