Mechanisms Underlying the Control of Progesterone Receptor Transcriptional Activity by SUMOylation

Abstract

Posttranslational modification by small ubiquitin-like modifier (SUMO) is a major regulator of transcription. We previously showed that progesterone receptors (PR) have a single consensus KXE SUMO-conjugation motif centered at Lys-388 in the N-terminal domain of PR-B and a homologous site of PR-A. SUMOylation of the PR is hormone-dependent and has a suppressive effect on transcription of an exogenous promoter. Here we show that repression of PR activity by SUMOylation at Lys-388 is uncoupled from phosphorylation, involves synergy between tandem progesterone response elements, and is associated with lowered ligand sensitivity and slowed ligand-dependent down-regulation. However, paradoxically, cellular overexpression of SUMO-1 increases PR transcriptional activity even if Lys-388 is mutated, suggesting that the receptors are activated indirectly by other SUMOylated proteins. One of these is the coactivator SRC-1, whose binding to PR and enhancement of agonist-dependent N-/C-terminal interactions is augmented by the presence of SUMO-1. Increased transcription due to SRC-1 is independent of PR SUMOylation based on assays with the Lys-388 mutants and the pure antiprogestin ZK98299, which blocks N-/C-terminal interactions. In summary, SUMOylation tightly regulates the transcriptional activity of PR by repressing the receptors directly while activating them indirectly through augmented SRC-1 coactivation.

RSRC1 SUMOylation enhances SUMOylation and inhibits transcriptional activity of estrogen receptor β

“…SUMOylation of some transcription factors fine-tunes their actions [21][22][23][24][25][26][27]. As previously reported [17], ERb SUMOylation inhibited its transcriptional activity because the ERb(K4R) mutant in which the ERb SUMOylation site was mutated increased estrogen-responsive element-containing luciferase (ERE-Luc) reporter activity compared to wild-type ERb in ERb-negative HEK293T cells (Fig.…”

“…These data indicate that ERb is a new substrate of PIAS1 and PIAS1 is essential for ERb SUMOylation. Many steroid hormone receptors, including ERa, ERb, androgen receptor (AR), progesterone receptor (PR), glucocorticoid receptor (GR), and mineralocorticoid receptor (MR), have been reported to be modified by SUMOylation (17,(21)(22)(23)(24)(25)(26)(27). AR, PR, GR, and MR are SUMOylated at a lysine residue embedded in the SUMOylation consensus sequence, whereas ERa and ERb are SUMOylated at a non-consensus lysine residue.…”

Regulation of the Structurally Dynamic N-terminal Domain of Progesterone Receptor by Protein-induced Folding

“…The NTDs of SRs are predicted by computational analysis to contain a high percentage of random coil, and solution phase biophysical analyses have directly confirmed the IDP characteristics of isolated NTDs of several SRs (22)(23)(24)(25)(26)(27)(28). NTDs of selected SRs have also been observed to undergo an increase in overall secondary and tertiary structure in the presence of natural osmolytes such as trimethylamine-N-oxide (TMAO) and trehalose (10,12,14,29).…”

Lysine Methylation of Progesterone Receptor at Activation Function 1 Regulates both Ligand-independent Activity and Ligand Sensitivity of the Receptor

“…We also examined if Lys-464 mutation alters functional interaction with SRC-1 (steroid receptor coactivator), a bona fide nuclear receptor co-activator that is known to functionally interact with both AF-1 and AF-2 of PR (16,50,51). There was an about 600-fold increase of R5020-induced PRB-K464Q activity in cells co-transfected with 10 ng of SRC-1 compared with empty vector control.…”