TRANSCRIPTION FACTORS AND ALDOLASE-B GENE-EXPRESSION IN MICRODISSECTED RENAL PROXIMAL TUBULES AND DERIVED CELL-LINES

Renal expression of the aldolase B isoenzyme and transcription factors previously shown to regulate the aldolase B gene promoter in the live r were analyzed in whole kidney, microdissected tubules, and the two P KSV-PCT and PKSV-PR proximal tubule cell lines derived from transgenic mice. Aldolase B gene expression appeared restricted to the proximal tubule, the site where HNF1 alpha, HNF1 beta, C/EBP alpha, and DBP tra nscripts were also abundant. Compared to the liver, another organ synt hesizing aldolase B, proximal tubules from the kidney were characteriz ed by the absence of HNF3 and the presence of higher ratio of HNF1 bet a/HNF1 alpha transcripts. The same features were conserved in both PKS V-PCT and PKSV-PR proximal tubule cell lines. Transactivation experime nts in PKSV-PCT cultured cells showed that HNF1 alpha, C/EBP alpha, an d DBP behave as transactivators of the 190-bp aldolase B gene promoter , and that HNF1 beta had a low transactivating efficiency. HNF1 beta, as well as HNF3, antagonized the HNF1 alpha-dependent transactivation of the aldolase B promoter. The fact that both HNF1 beta and HNF3 fact ors play similar negative roles by competitively binding close to or o n the HNF1 site could suggest that, in proximal tubule renal cells, HN F1 beta has the same attenuator effect on the aldolase B gene promoter as HNF3 in hepatocytes. Thus, these results indicate that such models of established renal tubule cell lines, which have conserved the same features of parental cells, represent valuable tools for studies of t he regulation of genes expressed in proximal tubules of the kidney. (C ) 1995 Academic Press, Inc.