The JmjC-containing lysine demethylase, KDM4D, demethylates di-and tri-methylation of histone H3 on lysine 9 (H3K9me3). How KDM4D is recruited to chromatin and recognizes its histone substrates remains unknown. Here, we show that KDM4D binds RNA independently of its demethylase activity. We mapped two non-canonical RNA binding domains: the first is within the N-terminal spanning amino acids 115 to 236, and the second is within the C-terminal spanning amino acids 348 to 523 of KDM4D. We also demonstrate that RNA interactions with KDM4D N-terminal region are critical for its association with chromatin and subsequently for demethylating H3K9me3 in cells. This study implicates, for the first time, RNA molecules in regulating the levels of H3K9 methylation by affecting KDM4D association with chromatin.

KDM4D is a lysine demethylase that removes tri-and di-methylated residues from H3K9 and is involved in transcriptional regulation and carcinogenesis. We recently showed that KDM4D is recruited to DNA damage sites in a PARP1-dependent manner and facilitates double-strand break repair in human cells. Moreover, we demonstrated that KDM4D is an RNA binding protein and mapped its RNA-binding motifs. Interestingly, KDM4D-RNA interaction is essential for its localization on chromatin and subsequently for efficient demethylation of its histone substrate H3K9me3. Here, we provide new data that shed mechanistic insights into KDM4D accumulation at DNA damage sites. We show for the first time that KDM4D binds poly(ADP-ribose) (PAR) in vitro via its C-terminal region. In addition, we demonstrate that KDM4D-RNA interaction is required for KDM4D accumulation at DNA breakage sites. Finally, we discuss the recruitment mode and the biological functions of additional lysine demethylases including KDM4B, KDM5B, JMJD1C, and LSD1 in DNA damage response.

The adherens junctions (AJs) and tight junctions (TJs) provide critical adhesive contacts between neighboring epithelial cells and are crucial for epithelial adhesion, integrity, and barrier functions in a wide variety of tissues and organisms. The striatin protein family, which are part of the striatin interaction phosphatases and kinases complex, are multidomain scaffolding proteins that play important biologic roles. We have previously shown that striatin colocalizes with the tumor suppressor protein adenomatous polyposis coli in the TJs of epithelial cells. Here we show that striatin affects junction integrity and cell migration, probably through a mechanism that involves the adhesion molecule E‐cadherin. Cells engaged in cell—cell adhesion expressed a high MW‐modified form of striatin that forms stable associations with detergent‐insoluble, membrane‐bound cellular fractions. In addition, striatin has recently been suggested to be a target of the poly (ADP‐ribose) polymerases Tankyrase 1, and we have found that striatin interacts with Tankyrase 1 and is subsequently poly‐ADP‐ribosylated. Taken together, our results suggest that striatin is a novel cell—cell junctional protein that functions to maintain correct cell adhesion and may have a role in establishing the relationship between AJs and TJs that is fundamental for epithelial cell—cell adhesion.—Lahav‐Ariel, L., Caspi, M., Nadar‐Ponniah, P. T., Zelikson, N., Hofmann, I., Hanson, K. K., Franke, W. W., Sklan, E. H., Avraham, K. B., Rosin‐Arbesfeld, R. Striatin is a novel modulator of cell adhesion. FASEB J. 33, 4729–4740 (2019). http://www.fasebj.org

No abstract

Since 1999, the COCH gene encoding cochlin, has been linked to the autosomal dominant non-syndromic hearing loss, DFNA9, with or without vestibular abnormalities. The hearing impairment associated with the variants affecting gene function has been attributed to a dominant-negative effect. Mutant cochlin was seen to accumulate intracellularly, with the formation of aggregates both inside and outside the cells, in contrast to the wild-type cochlin that is normally secreted. While additional recessive variants in the COCH gene (DFNB110) have recently been reported, the mechanism of the loss-of-function (LOF) effect of the COCH gene product remains unknown. In this study, we used COS7 cell lines to investigate the consequences of a novel homozygous frameshift variant on RNA transcription, and on cochlin translation. Our results indicate a LOF effect of the variant and a major decrease in cochlin translation. This data have a dramatic impact on the accuracy of genetic counseling for both heterozygote and homozygote carriers of LOF variants in COCH.