Differential stress induction of individual Alu loci: implications for transcription and retrotransposition

While human Alu repeats can be considered to be members of an extremely lar ge, globally regulated, multigene family, each member of this family reside s within a different sequence context that might uniquely modulate its tran scription. Unique 3' flanking sequences for several transcriptionally activ e human Alu elements were identified by cDNA cloning and used for primer ex tension analysis to compare the basal and stress-induced expression of the corresponding Aln loci. Each of six Alu loci investigated exhibits a unique pattern of expression in three different human cell lines and in response to stress induction. The sequence context surrounding each Alu member uniqu ely determines its transcriptional regulation. In many cases, the individua l Ain loci and total Alu RNA exhibit opposing patterns of expression implyi ng that local rather than global regulation ultimately determines the expre ssion of individual members. Some of the stresses, which induce Alu transcr iption, increase co-expression of LINE1 RNA, another requirement for Alu re trotransposition. (C) 2001 Elsevier Science B.V. All rights reserved.