Additional sex comb-like 1 (ASXL1), in cooperation with SRC-1, acts as a ligand-dependent coactivator for retinoic acid receptor.
Additional sex comb-like 1 (ASXL1, 170 kDa), a mammalian homolog of Drosophila ASX, was identified as a protein that interacts with retinoic acid receptor (RAR) in the presence of retinoic acid (RA). Systematic binding assays showed that the C-terminal nuclear receptor box (LVMQLL) of ASXL1 and the activation function-2 activation domain (AF-2 AD) core of the RAR are critical for ligand-dependent interaction. The interaction was confirmed using in vitro glutathione S-transferase pulldown and in vivo immunoprecipitation (IP) assays. Confocal microscopy revealed that ASXL1 localizes in the nucleus. In addition to the intrinsic transactivation function of ASXL1, its cotransfection together with an RA-responsive luciferase reporter increased the RAR activity. This ASXL1 activity appears to be mediated through the functional cooperation with SRC-1, as shown by GST pulldown, IP, chromatin IP, and transcription assays. In the presence of ASXL1, more acetylated histone H3 was accumulated on the RA-responsive promoter in response to RA. Finally, stable expression of ASXL1 increased the expression of endogenous RA-regulated genes and enhanced the antiproliferative potential of RA. Overall, these results suggest that ASXL1 is a novel coactivator of RAR that cooperates with SRC-1 and implicates it as a potential antitumor target of RA in RA-resistant cancer cells.
Cho
Yang-Sook
YS
Department of Bioscience and Biotechnology, Institute of Bioscience, Sejong University, 98 Kunja-dong, Kwangjin-gu, Seoul 143-747, Korea.
Kim
Eun-Joo
EJ
Park
Ui-Hyun
UH
Sin
Hong-Sig
HS
Um
Soo-Jong
SJ
D000595:Amino Acid Sequence; D000818:Animals; D001943:Breast Neoplasms; D002455:Cell Division / Q000502:physiology; D006367:HeLa Cells; D051548:Histone Acetyltransferases; D006801:Humans; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D056920:Nuclear Receptor Coactivator 1; D017434:Protein Structure, Tertiary; D018168:Receptors, Retinoic Acid / Q000737:chemistry / Q000378:metabolism*; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000072482:Retinoic Acid Receptor alpha; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000502:physiology; D020798:Two-Hybrid System Techniques
C510915:Asxl1 protein, mouse; D008024:Ligands; C000607071:RARA protein, human; C000607072:Rara protein, mouse; D018168:Receptors, Retinoic Acid; D012097:Repressor Proteins; D000072482:Retinoic Acid Receptor alpha; D014157:Transcription Factors; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; C538861:Ncoa1 protein, mouse; D056920:Nuclear Receptor Coactivator 1