Anatomy of an unusual RNA polymerase II promoter containing a downstream TATA element.
The adenovirus type 2 IVa2 promoter lacks a conventional TATA element yet directs transcription from two closely spaced initiation sites. To define elements required for in vitro transcription of this promoter, IVa2 templates carrying 5' deletions or linker-scanning mutations were transcribed in HeLa whole-cell extracts and the transcripts were analyzed by primer extension. Mutation of the sequence centered on position -47, which is specifically recognized by a cellular factor, reduced the efficiency of IVa2 transcription two- to threefold, whereas mutation of the sequence centered on position -30 selectively impaired utilization of the minor in vivo initiation site. Utilization of the major in vivo site was decreased no more than fivefold by deletion of all sequences upstream of position -15. By contrast, mutation of the region from +13 to +19 or of the initiation region severely impaired IVa2 transcription. The sequence spanning the initiation sites was sufficient to direct accurate initiation by RNA polymerase II from the major in vivo site. Thus, the two initiation sites of the IVa2 promoter are specified by independent elements, and a downstream element is the primary determinant of efficient transcription from both of these sites. The downstream element identified by mutational analysis altered the TATA element-like sequence TATAGAAA lying at positions +21 to +14 in the coding strand. Transcription from the wild-type IVa2 promoter was severely inhibited when endogenous TFIID was inactivated by mild heat treatment. Exogenous human TATA-binding protein (TBP) synthesized in Escherichia coli restored specific IVa2 transcription from both initiation sites when added to such heat-treated extracts. Although efficient IVa2 transcription requires both the downstream TATA sequence and active TFIID, bacterially synthesized TBP also stimulated the low level of IVa2 transcription observed when the TATA sequence was mutated to a sequence that failed to bind TBP.
Kasai
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Y
Department of Molecular Biology, Princeton University, New Jersey 08544-1014.
Chen
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H
Flint
S J
SJ
D000260:Adenoviruses, Human / Q000235:genetics*; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004279:DNA, Viral / Q000235:genetics*; D015967:Gene Expression Regulation, Viral; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D016385:TATA Box; D035362:Transcription Factor TFIID; D014157:Transcription Factors / Q000378:metabolism
D004279:DNA, Viral; D012333:RNA, Messenger; D035362:Transcription Factor TFIID; D014157:Transcription Factors; D012319:RNA Polymerase II