Studies of the mouse Rab geranylgeranyl transferase β subunit: Gene structure, expression and regulation

The mouse Rab geranylgeranyl transferase β (Rab GGTase β) catalytic subunit gene was isolated and characterized. This gene (Rabggtb) spans a distance of approx. 7 kb and is organized into eight exons. All the exon/intron junction sequences follow the GT/AG rule. Multiple transcription initiation sites are located within 384 bp upstream from the translation start codon. The 5'-flanking region contains several potential binding sites for transcription factors, but no TATA box is identified in this region. Expression of this gene was detected in all the major organs in adult animals. In mouse embryos, its expression was examined by in situ hybridization. Specific expression of this gene was elevated in mid-gestation stages, particularly developing liver and spinal cord. Northern blot analysis of an embryonic carcinoma cell line P19 showed that the steady-state level of Rabggtb mRNA expression was increased dramatically by cycloheximide (CHX) treatment as early as 2 h, suggesting a role of post-transcriptional regulation of Rab GGTase β gene expression. Actinomycin D was used to determine the half-life of Rab GGTase β transcripts. CHX treatment resulted in a dramatic increase of the half-life of Rab GGTase β transcripts, from 8 h to greater than 12 h.