Che-1/AATF-induced transcriptionally active chromatin promotes cell proliferation in multiple myeloma

Abstract

Multiple myeloma (MM) is a hematologic malignancy produced by a clonal expansion of plasma cells and characterized by abnormal production and secretion of monoclonal antibodies. This pathology exhibits an enormous heterogeneity resulting not only from genetic alterations but also from several epigenetic dysregulations. Here we provide evidence that Che-1/AATF (Che-1), an interactor of RNA polymerase II, promotes MM proliferation by affecting chromatin structure and sustaining global gene expression. We found that Che-1 depletion leads to a reduction of “active chromatin” by inducing a global decrease of histone acetylation. In this context, Che-1 directly interacts with histones and displaces histone deacetylase class I members from them. Strikingly, transgenic mice expressing human Che-1 in plasma cells develop MM with clinical features resembling those observed in the human disease. Finally, Che-1 downregulation decreases BRD4 chromatin accumulation to further sensitize MM cells to bromodomain and external domain inhibitors. These findings identify Che-1 as a promising target for MM therapy, alone or in combination with bromodomain and external domain inhibitors.

CK2-mediated phosphorylation of Che-1/AATF is required for its pro-proliferative activity

“…As previously observed, Che-1 displayed to have a key role in MM cells proliferation (14). To assess whether this effect could also be observed in other tumor cells of different origins, we performed cell proliferation analysis in HCT116, HeLa, 293T and U2OS cells, depleted or not for Che-1 expression.…”

“…1D). It has been shown that Che-1 depletion produces a global reduction of histone acetylation in MM cells (14). To extend these ndings, we performed WB analyses in several tumor cell lines depleted or not for Che-1 expression, observing that the loss of Che-1 expression produced a strong reduction in both H3 and H4 histone acetylation (Fig.…”

“…Detection of both heterochromatic foci and chromatin modi cations was performed as described in Bruno et al (14). Brie y, HCT116 cells were grown on cover-lips, washed twice in PBS, xed in 100% methanol for 5 min and then permeabilized for one hour with 1% BSA, 10% normal goat serum, 0.3 M glycine in 0.1% PBS-Tween.…”

“…Brie y, HCT116 cells were seeded in 100mm plate and transiently transfected with Myc-Che-1 wt, Myc-Che-1 3S or empty vector. 24 h post transfection cells were subjected to the protocol described in Bruno et al (14).…”

“…Importantly, Che-1 contains an acidic region spanning from 308 to 325 aa highly homologous to HDAC proteins and several viral oncoproteins (SV40 Large T, E1A) by which it contacts Rb, thus inhibiting its binding to HDAC 1 and promoting cell proliferation (11,13). More recently, we have demonstrated that this region is required for displacing HDAC proteins from histones, increasing chromatin accessibility and MM cell proliferation (14). Che-1 half-life and functions are modulated by several post-translational modi cations (12,15,16), and its phosphorylation at speci c serine or threonine residues has been associated with Che-1 activity in response to different stimuli, including induction of DNA damage or apoptosis (6,17).…”