An alternative retinoic acid-responsive Stra6 promoter regulated in response to retinol deficiency.

Abstract

Cellular uptake of vitamin A (retinol) is essential for many biological functions. The Stra6 protein binds the serum retinol-binding 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 ∼ 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 RARγ and RXRα 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 RARγ. In the brains of WT mice, both the longer and the shorter Stra6 transcript (Stra6L and Stra6S, respectively) are highly expressed, whereas these transcripts are found only at low levels in RARγ(-/-) mice. In the brains of vitamin A-deficient mice, both Stra6L and Stra6S levels are decreased. In contrast, in the vitamin A-deficient kidneys, the Stra6L levels are greatly increased, whereas Stra6S 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.

• Authors: Kristian B Laursen, Vasundhra Kashyap, Joseph Scandura, Lorraine J Gudas
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 290 Issue 7 Pg. 4356-66 (Feb 13 2015) ISSN: 1083-351X [Electronic] United States
• PMID: 25544292 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Chemical References

• Membrane Proteins
• Protein Isoforms
• RNA, Messenger
• Receptors, Retinoic Acid
• Stra6 protein, mouse
• Tretinoin

Topics

• Animals
• Base Sequence
• Blotting, Western
• Brain (metabolism)
• Cells, Cultured
• Chromatin Immunoprecipitation
• Embryonic Stem Cells (cytology, drug effects, metabolism)
• Epigenesis, Genetic
• Gene Expression Regulation
• Membrane Proteins (genetics, metabolism)
• Mice
• Mice, Inbred C57BL
• Mice, Knockout
• Molecular Sequence Data
• Promoter Regions, Genetic (genetics)
• Protein Isoforms
• RNA Splicing (genetics)
• RNA, Messenger (genetics)
• Real-Time Polymerase Chain Reaction
• Receptors, Retinoic Acid (physiology)
• Response Elements (genetics)
• Reverse Transcriptase Polymerase Chain Reaction
• Transcription Initiation Site
• Tretinoin (pharmacology)
• Vitamin A Deficiency
• Retinoic Acid Receptor gamma