Activation of the heregulin/HER2 pathway in oestrogen receptor (ER)-positive breast-cancer cells leads to suppression of oestrogen-receptor element (ERE)-driven transcription and disruption of oestradiol responsiveness, and thus contributes to progression of tumours to more invasive phenotypes. Here we report the identification of metastatic-associated protein 1 (MTA1), a component of histone deacetylase (HDAC) and nucleosome-remodelling complexes, as a gene product induced by heregulin-beta1 (HRG). Stimulation of cells with HRG is accompanied by suppression of histone acetylation and enhancement of deacetylase activity. MTA1 is also a potent corepressor of ERE transcription, as it blocks the ability of oestradiol to stimulate ER-mediated transcription. The histone-deacetylase inhibitor trichostatin A blocks MTA1-mediated repression of ERE transcription. Furthermore, MTA1 directly interacts with histone deacetylase-1 and -2 and with the activation domain of ER-alpha. Overexpression of MTA1 in breast-cancer cells is accompanied by enhancement of the ability of cells to invade and to grow in an anchorage-independent manner. HRG also promotes interaction of MTA1 with endogenous ER and association of MTA1 or HDAC with ERE-responsive target-gene promoters in vivo. These results identify ER-mediated transcription as a nuclear target of MTA1 and indicate that HDAC complexes associated with the MTA1 corepressor may mediate ER transcriptional repression by HRG.

The estrogen receptor plays an important role in breast cancer progression. Proline-, glutamic acid-, and leucine-rich protein 1 (PELP1), also called modulator of nongenomic activity of estrogen receptor (MNAR), a novel coactivator of estrogen receptor, modulates estrogen receptor transactivation functions. The mechanisms by which PELP1 modulates estrogen receptor genomic functions is not known. Here, using biochemical and scanning confocal microscopic analysis, we have demonstrated nuclear localization and functional implications of PELP1. Subnuclear fractionation showed PELP1 association with chromatin and nuclear matrix fractions. Ligand stimulation promoted recruitment of PELP1 to 17␤-estradiol responsive promoters, its colocalization with acetylated H3, and increased PELP1-associated histone acetyltransferase enzymatic activity. Far Western analysis revealed that PELP1 interacts with histone 1 and 3, with more preference toward histone 1. Using deletion analysis, we have identified the PELP1 COOH-terminal region as the histone 1 binding site. The PELP1 mutant lacking histone 1-binding domain acts as a dominantnegative and blocks estrogen receptor ␣-mediated transcription. Chromatin immunoprecipitation analysis showed a cyclic association and dissociation of PELP1 with the promoter, with recruitment of histone 1 and PELP1 occurring in opposite phases. PELP1 overexpression increased the micrococcal nuclease sensitivity of estrogen response element-containing nucleosomes. Our results provide novel insights about the transcription regulation of PELP1 and suggest that PELP1 participates in chromatin remodeling activity via displacement of histone 1 in cancer cells.

Elevated expression levels of the bcl-2 proto-oncogene have been extensively correlated with the appearance of androgen independence in prostate cancer. Although bcl-2 was first cloned as the t(14:18) translocation breakpoint from human follicular B cell lymphoma, the mechanism of overexpression of bcl-2 is largely undefined for advanced prostate cancer because there are no gross alterations in the gene structure. We investigated the role of the product of the prostate apoptosis response gene-4 (Par-4) and the product of the Wilms' tumor 1 gene (WT1) in the regulation of Bcl-2 expression in prostate cancer cell lines. We observed growth arrest and apoptosis, upon decreasing Bcl-2 protein and transcript in the high Bcl-2-expressing, androgen-independent prostate cancer cell line, by all-trans-retinoic acid treatment (ATRA), but this did not occur in the androgen-dependent cell line expressing low levels of Bcl-2. The decrease in the Bcl-2 protein and transcript following all-trans-retinoic acid treatment was accompanied by changes in localization of Par-4 and an induction in the expression of WT1 protein. In stable clones expressing ectopic Par-4 and in ATRA-treated cells, we observed decreased Bcl-2 protein and transcript. This was accompanied by an induction in WT1 expression. The involvement of WT1 in the Par-4-mediated down-modulation of Bcl-2 was further defined by blocking endogenous WT1 expression, which resulted in an increase in Bcl-2 expression. Finally, we detected Par-4 and WT1 proteins binding to a previously identified WT1-binding site on the bcl-2 promoter both in vitro and in vivo leading to a decrease in transcription from the bcl-2 promoter. We conclude that Par-4 regulates Bcl-2 through a WT1-binding site on the bcl-2 promoter. These data also identify Par-4 nuclear localization as a novel mechanism for ATRA-mediated bcl-2 regulation.

The C-terminal binding protein 1 (CtBP) is a ubiquitous corepressor linking the recruitment of DNA- and histone-modifying proteins to sequence-specific DNA-binding proteins and facilitating gene regulation during development and oncogenesis. We describe here the binding, phosphorylation and functional regulation of CtBP by the p21-activated kinase 1 (Pak1). Pak1 phosphorylates CtBP selectively on Ser158 within a putative regulatory loop, triggering CtBP cellular redistribution and blocking CtBP corepressor functions. A S158A substitution in CtBP or Pak1 knockdown by short interference RNA blocked CtBP phosphorylation, redistribution and attenuation of CtBP corepressor functions in reporter and chromatin assays. In the presence of NADH, Pak1 superphosphorylates CtBP and inhibits CtBP dehydrogenase activity, suggesting that preferential phosphorylation of active CtBP may alter secondary structures and influence both enzymatic and corepressor functions. Pak1 regulation of CtBP represents a new model of corepressor regulation whereby cellular signaling cascades may influence gene expression in mammalian cells.

Steven‐Johnson syndrome (SJS) is a severe cutaneous adverse drug reaction. Its occurrence due to vaccines is scant. 1 We report a case of SJS caused by COVID‐19 vaccine in an adult. A 60‐year‐old male presented with complaints of fever, oral ulceration and skin rash three days after the first dose of COVID‐19 vaccine, for which he visited a local physician and was prescribed paracetamol and levocetrizine, inspite of which the symptoms were not controlled and gradually the rashes became generalised in distribution.