Biology subjects

Zepecki, J. P.

Publications and source records attributed to Zepecki, J. P..

2 recordsLinked to original sources

bioRxiv2024

Heterochromatin spreading in cancer cells through HDAC7 mediated histone H3.3 landscape reprogramming.

Class IIa histone deacetylases (HDACs) are a family of enzymes with minimal histone deacetylase activity but can function as multi-protein interaction hubs. Here we demonstrate the expression of HDAC7, a Class IIa HDAC family member, in glioblastoma tumor tissue from 84 patients, patient-derived glioma stem cells (GSCs) from six patients, and pediatric diffuse pontine glioma (DIPG) cells from three patients. HDAC7 binds to Histone H3.3 and interacts with H3.3 and HIRA on chromatin. Targeted downregulation of HDAC7 expression with a subtype-specific siRNA inhibits the interaction of H3.3 with HIRA while increasing the association of H3.3 with DAXX and H3K9me3. This results in H3.3 being deposited on H3K9me3+/DAPI+ heterochromatin nuclear foci. Inhibition of HDAC7 triggers H3K9me3+ heterochromatin spreading, increased H3K9me3 binding in the cancer genome, and significant alterations in gene expression. Using single molecule DNA fiber approach, we show that HDAC7 inhibition results in a significant increase in replication fork speed without affecting fork symmetry. This altered replication fork speed leads to replication stress, evidenced by phosphorylation of RPA2 and impact on global DNA synthesis, resulting in reduced EdU incorporation. Finally, HDAC7 depletion leads to reduced BRCA2 expression and increased sensitivity of cancer cells to DNA damaging agents. Taken together, these studies uncover the involvement of HDAC7 in the euchromatic H3.3 chaperone network and the effect of HDAC7 depletion on chromatin dynamics, inducing epigenetic restriction and DNA damage in cancer cells.

cancer biology↗

bioRxiv2020

miRNA-mediated loss of m6A increases nascent translation in glioblastoma

Within the glioblastoma cellular niche, glioma stem cells (GSCs) can give rise to differentiated glioma cells (DGCs) and, when necessary, DGCs can reciprocally give rise to GSCs to maintain the cellular equilibrium necessary for optimal tumor growth. Here, using ribosome profiling, transcriptome and m6A RNA sequencing, we show that GSCs from patients with different subtypes of glioblastoma share a set of transcripts, which exhibit a pattern of m6A loss and increased protein translation during differentiation. The target sequences of a group of miRNAs overlap the canonical RRACH m6A motifs of these transcripts, many of which confer a survival advantage in glioblastoma. Ectopic expression of the RRACH-binding miR-145 induces loss of m6A, formation of FTO/AGO1/ILF3/miR-145 complexes on a clinically relevant tumor suppressor gene (CLIP3) and significant increase in its nascent translation. Inhibition of miR-145 maintains RRACH m6A levels of CLIP3 and inhibits its nascent translation. This study highlights a critical role of miRNAs in assembling complexes for m6A demethylation and induction of protein translation during GSC state transition. Author SummaryCellular plasticity and epigenetic adaptation of human glioblastoma stem cells to the tumor microenvironment is a hallmark of this devastating disease. With our present work, we discover the relationship between miRNAs and the RNA methylation machinery in human glioblastoma and show how miRNA-induced loss of m6A results in increase in protein translation of clinically important transcripts during glioblastoma stem cell differentiation. Leveraging the dynamic functions of these miRNAs can be important in the design of optimal therapeutics targeted at cancer cell plasticity.

cancer biology↗