USP49-mediated histone H2B deubiquitination regulates HCT116 cell proliferation through MDM2-p53 axis

To Ub or not to Ub: The epic dilemma of histones that regulate gene expression and epigenetic cross-talk

A dynamic array of histone post-translational modifications (PTMs) regulate diverse cellular processes in the eukaryotic chromatin. Among them, histone ubiquitination is particularly complex as it alters nucleosome surface area fostering intricate cross-talk with other chromatin modifications. Ubiquitin signaling profoundly impacts DNA replication, repair, and transcription. Histones can undergo varied extent of ubiquitination such as mono, multi-mono, and polyubiquitination, which brings about distinct cellular fates. Mechanistic studies of the ubiquitin landscape in chromatin have unveiled a fascinating tapestry of events that orchestrate gene regulation. In this review, we summarize the key contributors involved in mediating different histone ubiquitination and deubiquitination events, and discuss their mechanism which impacts cell transcriptional identity and DNA damage response. We also focus on the proteins bearing epigenetic reader modules critical in discerning site-specific histone ubiquitination, pivotal for establishing complex epigenetic crosstalk. Moreover, we highlight the role of histone ubiquitination in different human diseases including neurodevelopmental disorders and cancer. Overall the review elucidates the intricate orchestration of histone ubiquitination impacting diverse cellular functions and disease pathogenesis, and provides insights into the current challenges of targeting them for therapeutic interventions.

Decoding the ubiquitin language: Orchestrating transcription initiation and gene expression through chromatin remodelers and histones

Eukaryotic transcription is a finely orchestrated process and it is controlled by transcription factors as well as epigenetic regulators. Transcription factors and epigenetic regulators undergo different types of posttranslational modifications including ubiquitination to control transcription process. Ubiquitination, traditionally associated with protein degradation, has emerged as a crucial contributor to the regulation of chromatin structure through ubiquitination of histone and chromatin remodelers. Ubiquitination introduces new layers of intricacy to the regulation of transcription initiation through controlling the equilibrium between euchromatin and heterochromatin states. Nucleosome, the fundamental units of chromatin, spacing in euchromatin and heterochromatin states are regulated by histone modification and chromatin remodeling complexes. Chromatin remodeling complexes actively sculpt the chromatin architecture and thereby influence the transcriptional states of genes. Therefore, understanding the dynamic behavior of nucleosome spacing is critical as it impacts various cellular functions through controlling gene expression profiles. In this comprehensive review, we discussed the intricate interplay between ubiquitination and transcription initiation, and illuminated the underlying molecular mechanisms that occur in a variety of biological contexts. This exploration sheds light on the complex regulatory networks that govern eukaryotic transcription, providing important insights into the fine orchestration of gene expression and chromatin dynamics.

Inhibitory effect of Lonicera japonica-derived exosomal miR2911 on human papilloma virus

ETHNOPHARMACOLOGICAL RELEVANCE

Lonicera japonica Thunb. has been used as a traditional medicinal herb in China for thousands of years for its heat-clearing and detoxification effects. In recent years, experimental and clinical studies have shown that some Lonicera japonica-containing Chinese medicine prescriptions have been used to treat intraepithelia neoplasia caused by human papilloma virus (HPV) infection. However, its bioactive molecules and mechanism of action have not been fully explored.

AIM OF THE STUDY

In this study, Lonicera japonica-derived exosomes was extracted and exosomal miR2911 was identified. Bioinformatic analysis indicated that miR2911 potentially binds to the sequence of HPV. The mechanism of miR2911 action on HPV and the effect of exosomal miR2911 on HPV-induced cervical cancer cells were investigated.

METHODS

The potential targets of miR2911 on the HPV sequence were predicted and confirmed by using RNAhybrid and dual-luciferase reporter assays. Lonicera japonica exosomes were characterized by transmission electronic microscopy and zeta sizer analysis. RT-qPCR was used to measure miR2911 concentration in various tissues and exosomes. Synthetic miR2911 and GFP-E6/E7 plasmids were transfected into HEK293T cells to examine the effect of miR2911 on E6/E7 gene expression. The effects of miR2911 on endogenous E6/E7 mRNA and protein levels were detected in HPV16/18-positive cervical cancer cells by RT-qPCR and Western blotting. The proliferation and apoptosis of CaSki, SiHa and HeLa cells by the treatment of miR2911 or miR2911-containing exosomes were examined by CCK8, colony formation and flow cytometry assays.

RESULTS

MiR2911 is found to be enriched in various Lonicera japonica tissues, and is stably present in Lonicera japonica-derived exosomes. It is observed that MiR2911 directly binds to E6 and E7 oncogenes of HPV16/18, leading to the suppression of their protein expression. In addition, the endogenous E6/E7 mRNA and protein levels were significantly decreased by using miR2911 treatment in HPV16/18-positive cervical cancer cells. Furthermore, both miR2911 and miR2911-containing exosomes inhibited cell proliferation of SiHa, CaSki and HeLa cells, meanwhile inducing the cell apoptosis through E6/E7-p53/Caspase3 axis.

CONCLUSION

Our findings indicate that miR2911, an active component present in Lonicera japonica exosomes, inhibits proliferation and induces apoptosis of cervical cancer cells by targeting the E6/E7 genes of HPV16/18. Thus, Lonicera japonica-derived exosomal miR2911 has implications for the development of novel therapeutic strategies for the treatment of HPV-associated cervical cancers.