Clusterin gene is predominantly regulated by histone modifications in human colon cancer and ectopic expression of the nuclear isoform induces cell death

Abstract

Clusterin (CLU) is an important glycoprotein involved in various cellular functions. Different reports have mentioned that the two isoforms of CLU; secretary (sCLU) and nuclear (nCLU) have opposite (paradoxical) roles in cancer development. sCLU provides pro-survival signal, whereas nCLU is involved in pro-apoptotic signaling. However, the molecular mechanism of CLU gene regulation is not clear as of yet. We hypothesize that CLU gene is regulated by DNA methylation and histone modifications and clusterin plays an important role in colon cancer. To evaluate the hypothesis, we investigated CLU expression in colon cancer tissues and DNA methylation and histone modification status of CLU gene promoter. It is apparent from immonohistology data that both benign and cancerous (primary and metastasis) formalin fixed paraffin embedded (FFPE) tissue samples exhibit CLU expression. However and interestingly only noncancerous tissue samples show nCLU expression. Ectopic expression of nCLU either by epigenetic modulators or by nCLU transfection is responsible for colon cancer cell death. To clarify the molecular mechanisms for regulation of expression of CLU isoforms, we have analyzed DNA methylation and histone modifications, such as histone H3K9me3, H3K27me3, H3K4me3, and H3K9AcS10P patterns around the CLU promoter. There is no remarkable change in the DNA methylation status upon treatment of the cells by AZA, TSA and SAM. Our findings clearly show that promoter histone H3K9me3 and H3K27me3 marks are elevated in comparison to H3K4me3 and H3K9AcS10P marks in colon cancer cell lines.

DNA methylation analysis on purified neurons and glia dissects age and Alzheimer’s disease-specific changes in the human cortex

“…This effect is independent of AD diagnosis indicating that the epigenetic changes in CLU are a sign of “natural aging” contributing to disease aetiology. In the human two distinct CLU isoforms have recently been described with opposing functions in cell survival and apoptosis [ 21 , 28 , 73 , 130 , 131 ]. Our data indicate that an alternative promoter becomes epigenetically “activated” in aged neurons and the expression of a pro-apoptotic CLU isoform may contribute to degeneration predominantly in the CNS.…”

Quantitative proteomics decodes clusterin as a critical regulator of paternal factors responsible for impaired compensatory metabolic reprogramming in recurrent pregnancy loss

“…While, on the other hand, the molecular mechanism of action for CLUS is although unclear as of yet, but evidence suggests DNA methylation and histone modification events predominantly regulate CLUS gene (Deb et al, 2015). Moreover, mammalian development is encountered with two windows for genome-wide DNA demethylation and remethylation ie one during gametogenesis and the other post-fertilisation.…”

“…Moreover, mammalian development is encountered with two windows for genome-wide DNA demethylation and remethylation ie one during gametogenesis and the other post-fertilisation. While, on the other hand, the molecular mechanism of action for CLUS is although unclear as of yet, but evidence suggests DNA methylation and histone modification events predominantly regulate CLUS gene (Deb et al, 2015). Several studies have demonstrated that during intrauterine development alterations in imprinting pattern of H19, IGF2 and IGF2R to be associated with placental and foetal developmental abnormalities (Buckberry, Bianco-Miotto, Hiendleder, & Roberts, 2012).…”

Ascorbate induces apoptosis in melanoma cells by suppressing Clusterin expression

“…Besides TETs-mediated DNA demethylation, ascorbate could also regulate histone demethylation by serving as a cofactor for the JmjC domain-containing histone demethylases, which, like TETs, also belong to the iron and 2-oxoglutarate -dependent dioxygenase family 36–38 . Both DNA demethylation and histone demethylation are involved in regulating CLU transcription 39, 40 , and potentially alternative splicing, which could be instrumental to explain the differential effect of ascorbate on secreted CLU and nuclear CLU. Thus, elucidating the detailed epigenetic, or other, mechanism of ascorbate in suppressing CLU expression, especially the secreted CLU isoform, is ensured in future studies.…”