HMG-R genes

Tittiger C., Blomquist G. J., Ivarsson P., Borgeson C. E. and Seybold S. J. (1999) Juvenile hormone regulation of HMG-R gene expression in the bark beetle, Ips paraconfusus (Coleoptera Scolytidae) implications for male aggregation pheromone biosynthesis. Cell. Mol. Life Sci. 55, 121-127. 

In most insects, pheromones are synthesized in specialized cells or tissues associated with the epidermis (Tillman et al., 1999). Biochemical analyses traced the localization of Scolytid pheromone accumulation to portions of the alimentary canal, particularly the hindgut (e.g. Borden et al., 1969 Byers, 1983), but the actual tissue source of pheromone components was unknown. Fortunately, the tight correlation of HMG-R gene expression with pheromone component biosynthesis meant that hybridization techniques could be used to map the location of pheromone biosynthesis. Northern blots provided the first maps, while in situ hybridizations definitively showed which tissues were elevating HMG-R mRNA in response to feeding or JH III treatment. As with endocrine regulation studies, the molecular and biochemical data complemented each other. 

Figure 7.4 Regulation of HMG-R and HMG-S expression in male Dendroctonus jeffreyi by JH III. The time course (A, B) and dose response (C) for each gene in mature (emerged) males was investigated by northern blotting. All values are relative to starved, untreated males. Each point represents the mean +/- standard error of three replicates, five isolated thoraces/sample. Reproduced from Tittiger et al. (2000, 2003) with permission.

Fig. 3.3 Relative basal expression levels of mevalonate pathway genes in adult male and female Ips pini. For all genes, mRNA levels were significantly higher in males (t-test, / <0.001). AACT, acetoacetyl-CoA thilase HMG-S, HMG-CoA synthase HMG-R, HMG-CoA reductase MPDC, mevalonate-5-diphosphate decarboxylase IPPI, isopentenyldiphosphate isomerase GPPS, geranyldiphosphate synthase FPPS,...

Karayan L, Qiu S, Betard C, Dufour R, Roederer G, Minnich A, et al. Response to HMG CoA reductase inhibitors in heterozygous familial hypercholesterolemia due to the 10-kb deletion ( French Canadian mutation ) of the LDL receptor gene. Arteriosder Thromb 1994 14 1258-1263. 

Nicolas, R.H. and Goodwin, G.H. (1996) Molecular cloning of polybromo, a nuclear protein containing multiple domains including five bromodomains, a truncated HMG-box, and two repeats of a novel domain. Gene 175, 233-240. 

Pauli, T.T., Carey, M., and Johnson, R.C. (1996) Yeast HMG proteins NHP6A/B potentiate promoter-specific transcriptional activation in vivo and assembly of preinitiation complexes in vitro. Genes Dev. 10, 2769-2781. 

Korth, K.L., Stermer, B.A., Bhattacharyya, M.K. and Dixon, R.A. (1997) HMG-CoA reductase gene families that differentially accumulate transcripts in potato tubers are developmentally expressed in floral tissues. Plant Mol Biol, 33, 545-51. 

Raising the cellular cholesterol content not only stops transcription of the genes encoding the cholesterol biosynthetic enzymes, but also leads to accelerated degradation of the rate-limiting enzyme, HMG-CoA reductase [19]. In cholesterol-depleted cells, HMG-CoA reductase is a stable protein that is degraded slowly (T, = 13 h) (J.R. Faust,... 

If cholesterol repletion simply stopped transcription of the HMG-CoA reductase gene, it would lead to a slow decline in HMG-CoA reductase enzyme activity owing to stability of the protein however, in presence of excess sterols or mevalonate, there is rapid = 3.6 h) (J.R. Faust, 1982) and selective degradation of the enzyme, which results in more precise control of cellular sterol synthesis. 

Figure 2. Up-stream W ni r.t (UPKs) organization of human, pig and rat mitochondrial HMC-CoA synthase genes. (A) The transcription start site, indicated by arrows, was determined by 5-RACE for the human and pig genes, and by primer extension and SI experiments for the rat gene. The functionality of PPRE was showed experimentally for the rat and pig gene. Human PPRE showed 17/19 identity with rat PPRE, The scale at the top is in nucleotides. (B) Rat mitochondrial HMG-CoA synthase PPRE is a NR RE. Proposed model for the action of COUP-TE I and HNF-4 on the rat gene.

---