Analysis of the effects of CRABP I expression on the RA-induced transcription mediated by retinoid receptors.
The involvement of cellular retinoic acid-binding protein I (CRABP I) in the RA signaling was investigated by examining its effects on the interaction of retinoid receptors (RARs and RXRs) with RA-response elements (RAREs) as well as on the RA-induced transcription mediated by retinoid receptors. Analysis of the expression of mouse CRABP I from a cDNA expression plasmid in COS-1 cells revealed that this protein was about 5-fold more abundant in cytosol than in nuclei. The identity and the localization of CRABP I in the cytoplasm as well as the nuclei were also confirmed by the immunoperoxidase staining of the transfected COS-1 cells with CRABP I-specific antibody. When the nuclear extract containing a 10-fold molar excess of CRABP I was incubated with RAR alpha extract in the presence of [3H]RA and resolved on an FPLC size-exclusion column, a 20% decrease in the bound radioactivity in the RAR alpha fraction was accompanied by a proportional increase in the CRABP I fraction. In contrast, the addition of CRABP I did not significantly affect the interaction of RAR alpha or RAR alpha-RXR alpha heterodimers with RAREs. Moreover, the coexpression of CRABP I in CV-1 cells did not markedly inhibit or enhance the transcription activated by RARs and RAR alpha-RXR alpha heterodimers under RA concentrations ranging from 10(-10) to 10(-6) M. These results demonstrate that CRABP I, while it might be important for RA homeostasis, is not directly involved in the retinoid receptor-mediated RA-signaling pathway.
Venepally
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Kettering-Meyer Laboratories, Southern Research Institute, Birmingham, Alabama 35255, USA.
Reddy
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LG
Sani
B P
BP
D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D002522:Chlorocebus aethiops; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003600:Cytosol / Q000378:metabolism; D015870:Gene Expression; D007150:Immunohistochemistry; D051379:Mice; D018168:Receptors, Retinoic Acid / Q000096:biosynthesis / Q000187:drug effects / Q000302:isolation & purification / Q000502:physiology*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D015398:Signal Transduction; D014157:Transcription Factors / Q000187:drug effects / Q000502:physiology*; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*; D014162:Transfection; D014212:Tretinoin / Q000378:metabolism / Q000494:pharmacology*
C000607072:Rara protein, mouse; D018168:Receptors, Retinoic Acid; D011994:Recombinant Proteins; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D014157:Transcription Factors; C082927:retinoic acid binding protein I, cellular; D014212:Tretinoin; D015500:Chloramphenicol O-Acetyltransferase