Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.1 (RNase)
 16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Retinoids are metabolites of vitamin A that can regulate gene expression in a range of embryonic and adult cell types. They do this by binding to nuclear receptors belonging to the steroid/thyroid hormone receptor superfamily of ligand-activated transcription factors. Vertebrates possess two classes of nuclear retinoid-receptor genes, each with three members. These are the RAR-alpha, RAR-beta and RAR-gamma genes and the RXR-alpha, RXR-beta and RXR-gamma genes. In this paper we show by cDNA cloning and ribonuclease protection that the chicken RXR-gamma gene gives rise to two mRNA species (RXR-gamma 1 and RXR-gamma 2) that differ at their 5' ends. The two mRNAs have different tissue distributions in the 10-day-old chick embryo. RXR-gamma 2 mRNA was present in the eye and dorsal root ganglia but was undetectable in the liver. In contrast, RXR-gamma 1 mRNA was present in liver, was undetectable in dorsal root ganglia and was just detectable in the eye, where it was much less abundant than RXR-gamma 2 mRNA. The predicted protein products of the RXR-gamma 1 and RXR-gamma 2 mRNAs differ at their N-termini, in a region thought to modulate transcriptional transactivation by the receptor. These results show that at least one of the retinoid-X-receptor (RXR) genes gives rise to more than one protein product, a principle previously established for the retinoic acid-receptor (RAR) genes. The existence of multiple RXR protein isoforms would increase the range of heterodimers formed between RXRs and other nuclear receptors, including RARs and the receptors for thyroid hormone, vitamin D and peroxisome proliferators. This could increase the diversity of transcriptional responses mediated by these molecules.
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PMID:The chicken retinoid-X-receptor-gamma gene gives rise to two distinct species of mRNA with different patterns of expression. 803 82

Retinoids, analogues of vitamin A, can reverse premalignant lesions and prevent second primary tumors in patients with head and neck squamous cell carcinoma (HNSCC). The effects of retinoids are mediated by retinoic acid receptors (RARs) and retinoid X receptors (RXRs), which act as ligand-activated transcription factors. The regulation of cell growth, differentiation and retinoid metabolism in normal, premalignant and malignant cells by retinoids is thought to be a result of their effects on gene expression. We investigated mRNA expression of RARs (alpha, beta, and gamma) and RXR-beta by means of RNase protection and related this to retinoic acid (RA)-induced growth inhibition and RA turnover in four HNSCC cell lines (UM-SCC-14C, UM-SCC-22A, UM-SCC-35 and VU-SCC-OE). An RA-resistant subline of UM-SCC-35 was generated by exposure to increasing concentrations of RA for 8 months (designated UM-SCC-35R). RA turnover was determined on the basis of decreasing RA levels in the cells and culture medium after exposure to 1 microM RA. We found that RAR-gamma mRNA expression was strongly correlated with RA-induced growth inhibition (p = 0.016, R = 0.92) and RA turnover (p = 0.041, R = 0.86). RAR-beta transcript levels were reduced in three of five cell lines compared with normal mucosa, and these did not correlate with RA-induced growth inhibition and RA turnover. Expression of RAR-alpha and RXR-beta was not substantially altered in any of the cell lines. These findings suggest that in HNSCC cell lines RAR-gamma is the most important retinoid receptor for regulation of RA turnover rate and RA-induced growth inhibition.
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PMID:Expression of retinoic acid receptor gamma correlates with retinoic acid sensitivity and metabolism in head and neck squamous cell carcinoma cell lines. 1134 May 68