SUMOylation inhibits SF-1 activity by reducing CDK7-mediated serine 203 phosphorylation.
Steroidogenic factor 1 (SF-1) is an orphan nuclear receptor selectively expressed in the adrenal cortex and gonads, where it mediates the hormonal stimulation of multiple genes involved in steroid hormone biosynthesis. SF-1 is the target of both phosphorylation and SUMOylation, but how these modifications interact or contribute to SF-1 regulation of endogenous genes remains poorly defined. We found that SF-1 is selectively SUMOylated at K194 in Y1 adrenocarcinoma cells and that although SUMOylation does not alter the subcellular localization of SF-1, the modification inhibits the ability of SF-1 to activate target genes. Notably, whereas SF-1 SUMOylation is independent of S203 phosphorylation and is unaffected by adrenocorticotropin (ACTH) treatment, loss of SUMOylation leads to enhanced SF-1 phosphorylation at serine 203. Furthermore, preventing SF-1 SUMOylation increases the mRNA and protein levels of multiple steroidogenic enzyme genes. Analysis of the StAR promoter indicates that blockade of SF-1 SUMOylation leads to an increase in overall promoter occupancy but does not alter the oscillatory recruitment dynamics in response to ACTH. Notably, we find that CDK7 binds preferentially to the SUMOylation-deficient form of SF-1 and that CDK7 inhibition reduces phosphorylation of SF-1. Based on these observations, we propose a coordinated modification model in which inhibition of SF-1-mediated transcription by SUMOylation in adrenocortical cancer cells is mediated through reduced CDK7-induced phosphorylation of SF-1.
Yang
Wei-Hsiung
WH
Department of Internal Medicine, Division of Metabolism, University of Michigan Medical School, Ann Arbor, Michigan 48109-2200, USA.
Heaton
Joanne H
JH
Brevig
Holly
H
Mukherjee
Sarmistha
S
Iñiguez-Lluhí
Jorge A
JA
Hammer
Gary D
GD
D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002522:Chlorocebus aethiops; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D008239:Lysine / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism*; D054339:Steroidogenic Factor 1 / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
D000324:Adrenocorticotropic Hormone; D018844:Cyclin-Dependent Kinases; D008239:Lysine; D010768:Phosphoserine; D012333:RNA, Messenger; D025841:Small Ubiquitin-Related Modifier Proteins; D054339:Steroidogenic Factor 1; C090586:Cdk7 protein, mouse