CLONING AND CHARACTERIZATION OF RABBIT LIVER UDP-GLUCURONOSYLTRANSFERASE CDNAS - DEVELOPMENTAL AND INDUCIBLE EXPRESSION OF 4-HYDROXYBIPHENYL UGT2B13

A polyclonal antibody generated against rabbit liver p-nitrophenol UDP -glucuronosyltransferase (UGT) was used to screen a rabbit liver cDNA expression library constructed in lambdagt11. A 500-base pair cDNA clo ne, termed pPNP, generated a fusion protein that was antigenic with th e antibody. Clone pPNP encoded the 3' region of a UGT. To identify lar ger recombinants, clone pPNP was used as a probe to screen a second cD NA library constructed in lambdaZAP. Two different cDNA clones were id entified by DNA sequence analysis. Based upon their predicted amino ac id sequence analysis, the clones encode transferases belonging to the UGT2 subfamily, and have been identified as UGT2B13 and UGT2B14. The p redicted N-terminal sequence of UGT2B13 is identical to that determine d for the purified rabbit liver estrone UGT. However, expression of th e UGT2B13 cDNA in COS-1 cells displayed no activity in the presence of estrone but efficiently conjugated 4-hydroxybiphenyl. Results of Sout hern blot analysis using the 5' divergent region of the UGT2B13 cDNA t hat encodes exon 1 demonstrates that multiple genes share sequence hom ology to UGT2B13, an observation which indicates that the estrone UGT and UGT2B 1 3 genes are encoded by separate alleles. When the 5' varia ble. regions of the cDNAs where used in Northern blot analysis, the ex pression of UGT2B 13 and UGT2B 14 were shown to be expressed primarily in adult rabbits. However, when neonatal rabbits were treated with ei ther dexamethasone or rifampicin, UGT2B13 mRNA levels were induced. Th e neonatal induction of UGT2B13 mRNA corresponded with similar increas es in 4-hydroxybiphenyl UGT activity. The expression and induction of UGT2B13 paralleled that of the developmentally regulated rabbit liver progesterone 6beta-hydroxylase P4503A6.