Wellcome Senior Research Fellow
Known among his colleagues and peers as JP, Jeyaprakash is a Wellcome Senior Research Fellow at the Wellcome Centre for Cell Biology, University of Edinburgh, UK. He completed his PhD on the understanding of molecular determinants of carbohydrate specificities of plant lectins in 2004 at the Indian Institute of Science, Bangalore with Prof. M. Vijayan. After his PhD, JP obtained Alexander von Humboldt and Marie-Curie Fellowships to work with Prof. Elena Conti at EMBL-Heidelberg and subsequently at the Max-Planck Institute of Biochemistry, Martinsried, Germany, where he became interested in understanding the molecular mechanisms of accurate cell division. In 2012, he started his independent research group supported by a Wellcome Career Development fellowship and was awarded a Wellcome Senior Research Fellowship in 2017. JP’s lab is interested in understanding structural level mechanistic details of processes regulating centromere inheritance and chromosome segregation. His major contributions thus far include the structural characterisation of the Chromosomal Passenger Complex and the Ska complex, key protein assemblies involved in the physical attachment of chromosomes to spindle microtubule during cell division.
Structural biology of cell division
Cell division is an essential biological process that ensures genome integrity by equally and identically distributing chromosomes to the daughter cells. Errors in cell division often result in daughter cells with inappropriate chromosome numbers, a condition associated with cancers and birth defects. Key events that determine the accuracy of cell division include centromere specification, kinetochore assembly, physical attachment of kinetochores to spindle microtubules and successful completion of cytokinesis. These cellular events are regulated by a number of mitotic molecular assemblies (including the Chromosomal Passenger Complex (CPC), KMN (Knl1-Mis12-Ndc80) network, the Ska complex, Spindle Assembly Checkpoint and the Anaphase Promoting Complex) involving an extensive network of protein-protein interactions.
Although much is known about the basic mechanisms of cell division, structural level mechanistic details of pathways regulating error free chromosome segregation are still emerging. In particular, a high-resolution understanding of centromere inheritance and how kinetochores employ dynamic protein interaction to harness the forces generated by spindle microtubules to drive chromosome segregation is yet to be obtained. To address these important questions requires an approach that integrates structural and functional methods capable of dissecting and probing individual roles of protein interactions mediated at varying timescale. We use molecular biology and biochemical approaches to characterize protein interactions in vitro, X-ray crystallography, Cross-linking/Mass spectrometry, Small Angle X-ray Scattering (SAXS) and Electron Microscopy for structural analysis and a combination of in vitro and cell-based in vivo functional assays using structure-guided mutations for functional characterization.
The specific questions that we aim to address currently are i) What is the molecular basis for the establishment and maintenance of CENP-A nucleosomes at centromeres? ii) How do the outer kinetochore microtubule binding components cooperate to facilitate spindle driven chromosome segregation? and iii) How CPC, a key player required for eliminating incorrect kinetochore-microtubule attachment is targeted to the kinetochore? We address these questions by characterizing protein complexes involved in centromere maintenance (Mis18 and Mis18-associated), physically coupling chromosomes to kinetochores (the Ska complexes and other outer kinetochore microtubule binding factors) and error-correction (CPC and its centromere/kinetochore receptors). The structural and functional insights from these studies will also provide new avenues for targeting specific protein-interactions to fight mitosis related human health disorders.
Our recent crystal structures of Cal1 bound to CENP-A/H4 heterodimer and CENP-C provided a mechanistic understanding of how Cal1 targets CENP-A/H4 to centromeres to maintain centromere identity. Our work revealed that Cal1 combines functions of human Mis18 complex and HJURP, through evolutionarily conserved and adaptive interactions, to target CENP-A/H4 to centromeres in a self-sufficient manner. (Medina-Pritchard et al., 2020).
Medina-Pritchard, B., Lazou, V., Zou, J., Byron, O., Abad, M. A., Rappsilber, J., Heun, P and Jeyaprakash, A. A. (2020) Structural Basis for Centromere Maintenance by Drosophila CENP-A Chaperone Cal1. EMBO J e103234. Doi:10.15252/embj.2019103234
Abad, M. A., Ruppert, J. G*., Buzuk, L*., Wear, M. A., Zou, J., Webb, K. M., Kelly, D. A., Voigt, P., Rappsilber, J., Earnshaw, W. C and Jeyaprakash, A. A. (2019) Direct Nucleosome Binding of Borealin Secures Chromosome Association and Function of the CPC. J Cell Biol 218, 3912-3925.
Spiller, F*., Medina-Pritchard, M*., Abad, M. A*., Wear, M. A., Molina, O., Earnshaw, W. C and Jeyaprakash, A. A. (2017) Molecular Basis for Cdk1 Regulated Timing of Mis18 Complex Assembly and CENP-A Deposition. EMBO Rep 18, 894-905. Doi:10.15252/embr.201643564
Top panel: Overview of cell cycle-controlled CENP-A dilution and enrichment at centromeres.
Bottom Panel: Cartoon summarising our recent structural work on Cal1-mediated centromere maintenance in flies: Cal1 targets CENP-A/H4 to centromeres by directly binding both CENP-A/H4 and centromere receptor CENP-C (Abad et al., 2019).