科研之友
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摘要
Cellular uptake of vitamin A (retinol) is essential for many biological functions. The Stra6 protein binds the serum retinolbinding protein, RBP4, and acts in conjunction with the enzyme lecithin: retinol acyltransferase to facilitate retinol uptake in some cell types. We show that in embryonic stem (ES) cells and in some tissues, the Stra6 gene encodes two distinct mRNAs transcribed from two different promoters. Whereas both are all-trans-retinoic acid (RA)-responsive in ES cells, the downstream promoter contains a half-site RA response element (RARE) and drives an similar to 13-fold, RA-associated increase in luciferase reporter activity. We employed CRISPR-Cas9 genome editing to show that the endogenous RARE is required for RA-induced transcription of both Stra6 isoforms. We further demonstrate that in ES cells, 1) both RAR gamma and RXR alpha are present at the Stra6 RARE; 2) RA increases co-activator p300 (KAT3B) binding and histone H3 Lys-27 acetylation at both promoters; 3) RA decreases Suz12 levels and histone H3 Lys-27 trimethylation epigenetic marks at both promoters; and 4) these epigenetic changes are diminished in the absence of RAR gamma. In the brains of WT mice, both the longer and the shorter Stra6 transcript (Stra6(L) and Stra6(S), respectively) are highly expressed, whereas these transcripts are found only at low levels in RAR gamma(-/-) mice. In the brains of vitamin A-deficient mice, both Stra6(L) and Stra6(S) levels are decreased. In contrast, in the vitamin A-deficient kidneys, the Stra6(L) levels are greatly increased, whereas Stra6(S) levels are decreased. Our data show that kidneys respond to retinol deficiency by differential Stra6 promoter usage, which may play a role in the retention of retinol when vitamin A is low.
- 出版日期2015-2-13
