Abstract
The mouse globin gene loci are collections of active genes and inactive pseudogenes1–4. Not only are the globin pseudogenes α3 and α4 not expressed in globin-producing cells3, but RNA polymerase II does not transcribe these templates in vitro in conditions in which transcription of the active genes (for example, α1) is initiated accurately1,5. To localize the globin gene promoter and to determine whether the pseudogenes are promoter mutants whose function can be rescued by replacing mutant sequences with the analogous wild-type DNA, we have now analysed the transcriptional activity of several truncated and hybrid templates constructed from active α1 and inactive α4 genes. Our results indicate that a 44-base pair (bp) stretch of DNA (spanning nucleotides −55 to −11) is sufficient to direct RNA polymerase II to initiate transcription accurately in vitro. However, transcription efficiency is increased if the stretch of α1-globin DNA at the capping/initiation site (from −10 to +7) is included as part of the promoter segment. Analysis of hybrid promoters constructed from the active and pseudogenes, α1 and α4, demonstrated that replacement of the pseudogene's capping/initiation site with that of the active gene (nucleotides −9 to +7) restores the pseudogene promoter function in vitro. In addition, transcription studies with two other hybrid promoters indicate that the pseudogene's capping/initiation site is not simply a negative control element, but that RNA polymerase II may actually recognize and interact with a segment of DNA up to 60 nucleotides long.
Published Version
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