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Molecular and Cellular Biology, March 2001, p. 1973-1985, Vol. 21, No. 6
Center for Gene Technology, Tallinn Technical
University, and National Institute of Chemical Physics and
Biophysics, Tallinn EE12618, Estonia
Received 28 August 2000/Returned for modification 27 October
2000/Accepted 19 December 2000
In the human genome, retrotranspositionally competent long
interspersed nuclear elements (L1Hs) are involved in the generation of
processed pseudogenes and mobilization of unrelated sequences into
existing genes. Transcription of each L1Hs is initiated from its
internal promoter but may also be driven from the promoters of adjacent
cellular genes. Here I show that a hitherto unknown L1Hs antisense
promoter (ASP) drives the transcription of adjacent genes. The ASP is
located in the L1Hs 5' untranslated region (5'UTR) and works in the
opposite direction. Fifteen cDNAs, isolated from a human
NTera2D1 cDNA library by a differential screening method, contained L1Hs 5'UTRs spliced to the sequences of known genes or
non-proteincoding sequences. Four of these chimeric transcripts, selected for detailed analysis, were detected in total RNA of different
cell lines. Their abundance accounted for roughly 1 to 500% of the
transcripts of four known genes, suggesting a large variation in the
efficiency of L1Hs ASP-driven transcription. ASP-directed transcription
was also revealed from expressed sequence tag sequences and confirmed
by using an RNA dot blot analysis. Nine of the 15 randomly selected
genomic L1Hs 5'UTRs had ASP activities about 7- to 50-fold higher
than background in transient transfection assays. ASP was
assigned to the L1Hs 5'UTR between nucleotides 400 to 600 by deletion
and mutation analysis. These results indicate that many L1Hs contain
active ASPs which are capable of interfering with normal gene
expression, and this type of transcriptional control may be widespread.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.6.1973-1985.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Antisense Promoter of Human L1 Retrotransposon
Drives Transcription of Adjacent Cellular Genes
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