Identification of a sixth promoter that directs the transcription of γ- glutamyl transpeptidase type III RNA in mouse

Document Type

Journal Article

Publication Date



Journal of Biological Chemistry








We have previously identified five promoters in the 5'-flanking region of the mouse γ-glutamyl transpeptidase (γGT) gene. We now report the localization of a sixth promoter that supports the transcription of type III RNA, the major γGT RNA in fetal liver. We made a fetal liver cDNA library enriched for γGT RNA and obtained 12 γGT type III-specific clones. The longest clone is consistent with a transcription start site for type III RNA at a position 5' to the type IV promoter and about 5 kilobase(s) (kb) 5' to the first coding exon. We estimated by ribonuclease protection assay that about 80% of the γGT mRNA in fetal liver was type III. Primer extension and nuclease protection analyses mapped the 5' end of type III mRNA in fetal liver and kidney to a single cluster of potential major and minor transcription start sites. Deletion analysis using transient expression of chloramphenicol acetyltransferase constructs of the type III promoter region revealed the greatest activity with a 1-kb 5'-flanking fragment in mouse kidney proximal tubular cells and no detectable activity in NIH-3T3 fibroblasts. These studies demonstrate that the type III 5' region of the mouse γGT gene is organized into two distinct exons (IIIa and IIIb) and that type III RNA is expressed under the control of its own promoter.

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