Cloning and characterisation of the first drug-metabolising canine UDP-glucuronosyltransferase of the 2B subfamily.

Glucuronidation is a major route of clearance for a diverse set of both drug and endogenous substrates. The present study was undertaken to redress the lack of molecular information currently available on drug glucuronidation by the dog, a species widely used in metabolism studies by the pharmaceutical industry. A novel dog uridine diphosphate glucuronosyltransferase (UGT), designated UGT2B31 (GenBank Accession Number: AY135176), has been isolated from a dog cDNA library, expressed in V79 cells and characterised using various methods: (i) UGT2B31 sequence has been compared with mammalian UGT sequences using both sequence alignments and phylogenetic analysis; and (ii) the substrate specificity of UGT2B31 has been determined using functional analysis and compared with that obtained using UGT2B7 and dog liver microsomes.

UBF binding in vivo is not restricted to regulatory sequences within the vertebrate ribosomal DNA repeat.

The HMG box containing protein UBF binds to the promoter of vertebrate ribosomal repeats and is required for their transcription by RNA polymerase I in vitro. UBF can also bind in vitro to a variety of sequences found across the intergenic spacer in Xenopus and mammalian ribosomal DNA (rDNA) repeats. The high abundance of UBF, its colocalization with rDNA in vivo, and its DNA binding characteristics, suggest that it plays a more generalized structural role over the rDNA repeat.