Investigating the functional domains of horma-domain protein HTP-1 during C. elegans meiosis
File(s)
Author(s)
Telecan, Oana Diana Petruta
Type
Thesis or dissertation
Abstract
Proper chromosome segregation during meiosis requires homologue recognition, synapsis and recombination during meiotic prophase, followed by two-step release of sister chromatid cohesion (SCC) during the meiotic divisions. All these events are promoted by a conserved family of HORMA-domain proteins, which associate with the chromosome axes at the start of meiotic prophase. In C. elegans, HORMA-domain protein HTP-1 promotes homologue pairing, participates in an early prophase checkpoint that monitors synaptonemal complex assembly, promotes the formation of inter-homologue crossover events during meiotic recombination, and, along with its paralogue HTP-2, prevents the premature release of SCC during the first meiotic division. However, the molecular mechanisms by which HTP-1 exerts its functions remain unknown. HTP-1 consists of a HORMA domain (~220 amino acids) that is structurally similar to the spindle assembly checkpoint protein Mad2 and from two additional N- and C-terminal domains extending from the HORMA domain whose role has previously remained uncharacterised. Here, I show that the HORMA-domain of HTP-1 is required for HTP-1 loading to axial elements by engaging into a physical interaction with HTP-3 and that this interaction is disrupted by a point mutation at M127. I also show that the HTP-1 N-terminal region (first 30 amino acids) is essential to prevent the precocious release of SCC during the first meiotic division by acting as a platform for recruitment of the PP1 phosphatase interactor LAB-1 to axial elements, locally antagonizing H3 T3 phosphorylation, a chromatin mark that recruits Aurora B. Finally, I assign a role for the C-terminus of HTP-1 in supporting the protein's functions in homologue pairing and synapsis checkpoints as well as in promoting initiation of recombination by acting as a regulator of the master kinase CHK-2. All in all, this study uncovers unexpected roles for the meiotic HORMADs as local regulators of histone modifications and of kinase activity.
Version
Open Access
Date Issued
2017-09
Date Awarded
2018-02
Copyright Statement
Creative Commons Attribution Non-Commercial No Derivatives
licence.
licence.
Advisor
Martinez-Perez, Enrique
Zhang, Xiaodong
Publisher Department
Institute of Clinical Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)