A SET OF POLYCLONAL AND MONOCLONAL-ANTIBODIES REVEALS MAJOR DIFFERENCES IN POSTTRANSLATIONAL MODIFICATION OF THE RAT HNF1 AND VHNF1 HOMEOPROTEINS

The related homeodomain-containing transcription factors HNF1 (HNF1 al pha) and vHNF1 (HNF1 beta) recognise common target DNA sequences in th e regulatory regions of many genes and are expressed in several parenc hymal cell types, predominantly in liver, kidney, intestine and pancre as. HNF1-null mutant mice. with a wild-type vHNF1 gene, develop normal ly, but die within a few weeks of birth with severe liver and kidney f ailure. Humans with a mutation in the HNF1 alpha gene develop non-insu lin dependent diabetes on maturity (MODY 3). To determine distinctive roles for each of these proteins we produced a set of polyclonal sera and monoclonal antibodies, directed against different parts of the rat HNF1 and vHNF1 proteins. These antibodies reveal that HNF1 is present in vivo as a heterogeneous mixture of 92-98 kDa molecular mass polype ptides, a mass higher than that expected from its amino acid sequence. vHNF1 is present in the form of two isoforms of roughly the expected molecular masses; 65 and 68 kDa. In addition, some antibodies prepared against bacterially-produced HNF1 recognise vHNF1 but not HNF1, in li ver and kidney extracts. Hence, we present the first evidence for diff erential post-translational modification of HNF1 and vHNF1 proteins.