Molecular mechanism for the potentiation of the transcriptional activity of human liver receptor homolog 1 by steroid receptor coactivator-1.
The liver receptor homolog 1 (LRH-1) belongs to the Fushi tarazu factor 1 nuclear receptor subfamily, and its biological functions are just being unveiled. The molecular mechanism for the transcriptional regulation by LRH-1 is not clear yet. In this report, we use mutagenesis and reporter gene assays to carry out a detailed analysis on the hinge region and the proximal ligand binding domain (LBD) of human (h) LRH-1 that possess important regulatory functions. Our results indicate that helix 1 of the LBD is essential for the activity of hLRH-1 and that the steroid receptor coactivator (SRC)-1 interacts directly with the LBD of hLRH-1 and significantly potentiates the transcriptional activity of hLRH-1. Cotransfection assays demonstrate that overexpressed SRC-1 potentiates hLRH-1 mediated activation of the cholesterol 7-alpha-hydroxylase promoter and increases the transcription of the endogenous cholesterol 7-alpha-hydroxylase in Huh7 cells. The interaction between SRC-1 and hLRH-1 assumes a unique pattern that involves primarily a region containing the glutamine-rich domain of SRC-1, and helix 1 and activation function-2 of hLRH-1 LBD. Mutagenesis and molecular modeling studies indicate that, similar to mouse LRH-1, the coactivator-binding cleft of hLRH-1 LBD is not optimized. An interaction between helix 1 of hLRH-1 LBD and a region containing the glutamine-rich domain of SRC-1 can provide an additional stabilizing force and enhances the recruitment of SRC-1. Similar interaction is observed between hLRH-1 and SRC-2/transcriptional intermediary factor 2 or SRC-3/acetyltransferase. Moreover, transcriptional intermediary factor 2 and acetyltransferase also potentiate the transcriptional activity of hLRH-1, suggesting a functional redundancy among SRC family members. These findings collectively demonstrate an important functional role of helix 1 in cofactor recruitment and reveal a novel molecular mechanism of transcriptional regulation and cofactor recruitment mediated by hLRH-1.
Xu
Ping-Long
PL
State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
Liu
Yun-Qing
YQ
Shan
Shi-Fang
SF
Kong
Yu-Ying
YY
Zhou
Qing
Q
Li
Mei
M
Ding
Jian-Ping
JP
Xie
You-Hua
YH
Wang
Yuan
Y
D000123:Acetyltransferases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D002790:Cholesterol 7-alpha-Hydroxylase / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D051548:Histone Acetyltransferases; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D056920:Nuclear Receptor Coactivator 1; D051958:Nuclear Receptor Coactivator 2; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011487:Protein Conformation; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; C082631:NR5A2 protein, human; D051958:Nuclear Receptor Coactivator 2; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D002790:Cholesterol 7-alpha-Hydroxylase; D000123:Acetyltransferases; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; C538861:Ncoa1 protein, mouse; D056920:Nuclear Receptor Coactivator 1