JAB1 Interacts with Both the Progesterone Receptor and SRC-1

Abstract

JAB1 (Jun activation domain-binding protein-1) has previously been described as a coactivator of AP1 transcription factor. We show here, by yeast and mammalian two-hybrid analyses and by pull-down experiments, that JAB1 also interacts with both the progesterone receptor (PR) and the steroid receptor coactivator 1 (SRC-1) and that it stabilizes PR-SRC-1 complexes. We also show that JAB1 potentiates the activity of a variety of transcription factors known to associate with SRC-1 (nuclear receptors, activator protein-1, and nuclear factor B). This occurs without any modification of PR or SRC-1 concentration. JAB1 is a subunit of a large multiprotein complex that has been called the COP9 signalosome. The latter is present in plant and animal cells and has been shown to be involved in a variety of cellular mechanisms including transcription regulation, cell cycle control, and phosphorylation cascades. We now show that it is also involved in the mechanisms of action of nuclear receptors and of their coactivators.JAB1 (Jun activation domain-binding protein-1) was initially isolated by a two-hybrid screen (1) using the c-Jun Nterminal activation domain as a bait. It was shown that JAB1 potentiates target gene transcription activation by AP1 proteins (especially c-Jun and JunD) (1). This initial study also pointed to the sequence homology between JAB1 and the yeast protein Pad-1. The latter has been demonstrated to be necessary for the transcriptional activity of Pap-1, the yeast equivalent of c-Jun (1, 2). Furthermore it was shown that JAB1 could functionally replace Pad-1 in yeast. Thus JAB1 and Pad-1 appeared to play similar roles in mammalian and yeast cells, respectively. However, recent studies have uncovered the true human homolog of Pad-1, which has been called POH-1. Both Pad-1 and POH-1 are components of the 26 S proteasome (3, 4).On the contrary JAB1 is not found in the proteasome but has very recently been shown to be a subunit of a different multiprotein complex that has been called the signalosome (or COP9 signalosome). This complex contains several proteins with sequence homologies to proteins present in the regulatory 19 S subunit of the 26 S proteasome (5-7). It has been proposed that the latter and the signalosome have a common evolutionary origin but have diverged to assume different cellular functions.Moreover recent studies have shown an interaction of Fos/ Jun with SRC-1. The latter potentiates AP1 1 -mediated gene transactivation (8). SRC-1, also called p160 and ERAP160 (9 -12) is a member of the large family of nuclear receptor coactivators including SRC-2 (also called TIF2 and GRIP1) (13, 14), SRC-3 (also called TRAM1, ACTR, AIB1, RAC3, and p/CIP) (15-19), and ARA-70 (androgen receptor-associated protein) (20). These proteins form complexes with nuclear receptors and CBP or p300 (12,16,19,(21)(22)(23)(24). The latter recruit into transcription complexes histone acetylases such as p300/CBP-associated factor (16,25,26). Coactivators CBP and p300 also have intrinsic histone acetylase activity. Histo...

Jab1 is overexpressed in human breast cancer and is a downstream target for HER-2/neu

“…Jab1 in the nucleus functions as transcription coactivator and may interact and modulate the activity of steroid receptors as demonstrated previously. 33,34 Our results indeed demonstrated a marginal correlation between Jab1 and estrogen receptor or progesterone receptor ( Table 2). The functional interaction between steroid receptors and Jab1 received much attention recently.…”

Steroid receptor coactivator 3 regulates autophagy in breast cancer cells through macrophage migration inhibitory factor

“…Intracellular MIF interacted with the signalosome component JAB1/CSN5 and was shown to regulate both the activity of tumor suppressor p53 and the angiogenesis induced by hypoxia [17,18]. Interestingly, JAB1/CSN5 was further shown to interact with PR and SRC-1 and potentiated the activity of a variety of transcription factors known to associate with SRC-1, such as AP-1 and NF-κB [19][20][21]. In addition, JAB1 expression was required for the rapid and transient activation of ERK by MIF, and the ability of JAB1/CSN5 to activate AP-1 is modulated by interaction with MIF [22,23].…”

The steroid receptor co-activator-1 (SRC-1) potentiates TGF-β/Smad signaling: role of p300/CBP

“…Tagged Smad3, Smad4, and Smad7 expression vectors (gifts from Dr A Roberts, NIH, Bethesda, MD, USA) were previously described (de Caestecker et al, 1998). Plasmids encoding the wild-type human SRC-1 (pSG5-HA-SRC-1) and deletion mutant (pSG5-HA-Dp300SRC-1) (kind gift from E Milgrom, INSERM U135, Le Kremlin-Bicetre, France), p300 (kind gift from Dr T Shioda, Boston, MA, USA), E1A and deletion mutant mE1A (gift from Dr A Roberts, NIH, Bethesda, MD, USA) have been previously described (respectively by Chauchereau et al, 2000;de Caestecker et al, 2000).…”

“…G5E1b-Lux containing five Gal4 binding sites driving the expression of luciferase and Gal4BD-Smad3 fusion protein expression vector, containing the full-length Smad3 cDNA have been described previously (Atfi et al, 1997). Additional expression vectors used in this study were: Gal4BD-p300 (a kind gift from Dr A Giordano, Thomas Jefferson University, Philadelphia, PA, USA) (Yuan et al, 1996) and VP16AD-SRC-1 (kind gift from E Milgrom, INSERM U135, Kremlin-Bicetre, France) (Chauchereau et al, 2000).…”

“…As shown in Figure 5c and d, p300 relieved E1A inhibition of SRC-1 effect on TGF-b-driven Smad3/4 specific promoter transactivation. To ascertain the role played by p300, we then tested the effect of a mutant form of SRC-1 laking the CBP/p300-binding site (Chauchereau et al, 2000) on Smad-dependent transcription. As shown in Figure 6a and b, expression of the truncated SRC-1 failed to enhanced TGF-b-driven (SBE) 4 -lux and p800-lux promoter transactivation, confirming the need for p300 in SRC-1-mediated enhancement of Smad3/4-dependent transcription.…”