Weitzman, J. | bioRxiv Science

bioRxiv2022

Putative SET-domain methyltransferases in Cryptosporidium parvum and histone methylation during infection

Cryptosporidium parvum is a major cause of an intestinal pathology called cryptosporidiosis which affects humans and other vertebrates. Despite being declared as a public health problem by World Health Organization (WHO) since 2006, pathogenesis caused by this parasite remains poorly understood. More recently, C. parvum has been linked with oncogenesis. In particular, the mechanisms involved in the processes of gene expression regulation are completely unexplored in Cryptosporidium. In the current study, we took the opportunity to investigate a dynamic epigenetic modification called histone lysine methylation during the life cycle of the parasite. We successfully identified putative SET-domain containing proteins, lysine methyltransferases (KMTs), which catalyze the methylation of different lysine residues. Phylogenetic analysis classified them into distinct subfamilies namely CpSET1, CpSET2, CpSET8, CpKMTox and CpAKMT. Structural analysis further characterized CpSET1, CpSET2 and CpSET8 to be histone lysine methyltransferases (HKMTs). Their functional significance was predicted by using site-specific methyl-lysine antibodies during development of the parasite (CpSET1:H3K4; CpSET2:H3K36; CpSET8:H4K20). In particular, the SET domain of CpSET8 showcased methyltransferase activity confirming the existence of functional HKMTs in Cryptosporidium. Moreover, the consequence of C. parvum infection on the host lysine methylation events highlights the inherit potential of the parasite to exploit the host epigenetic regulation to its advantage. Thus, this study is the first one to provide insights on epigenetics mechanisms occurring throughout the parasites life cycle and during the interaction with its host. As Cryptosporidium is a protozoan that significantly affects the health of both humans and animals, a better understanding of its developmental processes within the definitive host may highlight novel infection control strategies. Author SummaryCryptosporidium species have a very compact genome (~9.2 Mb) unlike its apicomplexan homologs such as Toxoplasma (~63 Mb). Moreover, the lack of large families of transcriptional factors requires them to heavily rely on chromatin remodeling components for its gene regulation. Thus, study and identification of novel elements which contribute to chromatin dynamics could assist a better understanding of the biology of this parasite. In the current study we investigated histone lysine methylation, a dynamic epigenetic modification which regulates gene activation as well as repression. More importantly, characterizing the enzymes which bring about this regulation, provides potential new druggable targets to attack the parasite.

microbiology↗

bioRxiv2020

The impact of cell geometry and the cytoskeleton on the nucleo-cytoplasmic localisation of the SMYD3 methyltransferase suggests that the epigenetic machinery is mechanosensitive

Mechanical cues from the cellular microenvironment are converted into biochemical signals controlling diverse cell behaviours, including growth and differentiation. But it is still unclear how mechanotransduction ultimately affects nuclear readouts, genome function and transcriptional programs. Key signaling pathways and transcription factors can be activated, and can relocalize to the nucleus, upon mechanosensing. Here, we tested the hypothesis that epigenetic regulators, such as methyltransferase enzymes, might also contribute to mechanotransduction. We found that the SMYD3 lysine methyltransferase is spatially redistributed dependent on cell geometry (cell shape and aspect ratio) in murine myoblasts. Specifically, elongated rectangles were less permissive than square shapes to SMYD3 nuclear accumulation, via reduced nuclear import. Notably, SMYD3 has both nuclear and cytoplasmic substrates. The distribution of SMYD3 in response to cell geometry correlated with cytoplasmic and nuclear lysine tri-methylation (Kme3) levels, but not Kme2. Moreover, drugs targeting cytoskeletal acto-myosin induced nuclear accumulation of Smyd3. We also observed that square vs rectangular geometry impacted the nuclear-cytoplasmic relocalisation of several mechano-sensitive proteins, notably YAP/TAZ proteins and the SETDB1 methyltransferase. Thus, mechanical cues from cellular geometric shapes are transduced by a combination of transcription factors and epigenetic regulators shuttling between the cell nucleus and cytoplasm.

biophysics↗