The rat facilitated glucose transporter gene. Transformation and serum-stimulated transcription initiate from identical sites

Abstract

The gene encoding the rat brain facilitated glucose transporter protein was cloned and partially sequenced. The transcribed regions encode 10 exons that span about 30 kilobases of genomic DNA. The intron size is markedly biased, the first two significantly greater in length than the seven others. All of the introns are predicted to occur in regions that encode putative extramembranous domains of the protein, consistent with the proposed topology of 12 alpha-helical membrane-spanning segments. In brain, transcription of the glucose transporter gene initiates at two adjacent adenosine residues located about 30 base pairs 3' to a TATA sequence. In addition, there is at least one minor upstream start site. Both transformation of fibroblasts by the oncogenic retrovirus Fujinami sarcoma virus and stimulation of quiescent fibroblasts with serum increase transcription of the glucose transporter gene from identical initiation sites, which are the same as the predominant start sites in brain. The use of the same promoter for increased transcription under both conditions is consistent with the hypothesis that the regulation of gene expression by normal growth and by oncogenesis is mediated by similar or identical pathways.