Wellcome Principal Research Fellow
Robin Allshire is a Wellcome Principal Research Fellow and Professor of Chromosome Biology at the University of Edinburgh. After graduating from Trinity College Dublin, Ireland in 1981 with a BA in Genetics, he obtained a Royal Commission for the Exhibition of 1851 scholarship and studied for a PhD at the MRC Mammalian Genome Unit, Edinburgh (MRC HGU) with Dr. Chris Bostock and Ed Southern. Following post-doctoral research at the MRC HGU with Prof. N.D. Hastie, he began his independent research career in 1989 at Cold Spring Harbor Laboratories, New York. He returned to a tenured position at MRC HGU from 1990 to 2002 during which he took a three month research sabbatical with Prof. Mitsuhiro Yanagida at Kyoto University. In 2002, he moved to the Wellcome Centre for Cell Biology where he runs a dynamic research group as a Wellcome Principal Research Fellow (2002-2022). He was elected a member of the European Molecular Biology Organisation (EMBO) in 1998, a fellow of the Royal Society of Edinburgh (FRSE) in 2005 and a fellow of the Royal Society (FRS), London in 2011. He was awarded the Genetics Society (UK) Medal in 2013.
Epigenetic inheritance: establishment and transmission of specialised chromatin domains
Chromosomal DNA is wrapped around nucleosomes containing core histones (H3/H4/H2A/H2B). However, at centromeres a specific histone H3 variant, CENP-A, replaces histone H3 to form specialized CENP-A nucleosomes. CENP-A chromatin is critical for assembly of the chromosome segregation machinery – kinetochores – at these specific chromosomal locations and is flanked by histone H3 lysine 9 methylated heterochromatin.
Our goal is to decipher conserved mechanisms that establish, maintain and regulate the assembly of heterochromatin and CENP-A chromatin domains. Heterochromatin is required for the establishment of CENP-A chromatin on centromere DNA. One objective is to provide further insight into mechanisms that promote heterochromatin formation on pericentromeric repeats. Heterochromatin might also silence genes throughout the genome, we therefore also investigate how heterochromatin formation is regulated and whether such mechanisms influence phenotype. We endeavour to determine how heterochromatin, spatial nuclear organisation and non-coding RNAPII transcription combine to mediate CENP-A incorporation at centromeres.
Our main questions are:
1. How do DNA, RNA and chromatin signatures instigate the assembly of specialized chromatin domains?
2. How does chromatin architecture and subnuclear compartmentalization affect specialized chromatin domains?
3. How does heterochromatin influence gene expression?
Previously we showed that non-homologous centromere DNA from other fission yeast species is recognised and can direct functional centromere assembly in standard laboratory fission yeast, Schizosaccharomyces pombe (Tong, Pidoux et al. 2019). This suggested that conserved processes recognize features associated with non-conserved centromere DNA allowing preservation of centromere identity and location over evolutionary time. Conserved processes such as transcription may allow sequence divergence but preservation of template driven events such as non-coding transcription (Shukla et al 2018). Affinity selection of centromere specific CENP-A-tagged chromatin showed strong enrichment of all subunits of the Ino80 chromatin remodeling complex, including its non-essential, auxiliary component Hap2 (Figure A). Wild-type cells, but not cells lacking Hap2, can establish CENP-A chromatin and functional centromeres on naïve minichromosomes introduced as naked DNA (Figure B). Centromeric DNA, that has not assembled CENP-A chromatin exhibits reduced turnover of histone H3 (see Singh et al. 2020) and transcription from embedded promoters (cc2-ProA, B, C) in cells lacking Hap2 (Singh et al 2020; Figure C). Our analyses suggest that the Hap2-Ino80 Complex destabilizes H3 nucleosomes on centromere DNA through transcription-coupled histone H3 turnover, driving the replacement of resident H3 nucleosomes with CENP-A nucleosomes (Figure D). It is likely that such inherent properties define centromere DNA by directing a program that mediates CENP-A assembly on appropriate sequences.
Shukla, M., Tong, P., White, S.A., Singh, P.P., Reid, A.M., Catania, S., Pidoux, A.L., and Allshire, R.C. (2018). Centromere DNA Destabilizes H3 Nucleosomes to Promote CENP-A Deposition during the Cell Cycle. Curr Biol 28, 3924–3936.
Tong, P., Pidoux, A.L., Toda, N.R.T., Ard, R., Berger, H., Shukla, M., Torres-Garcia, J., Müller, C.A., Nieduszynski, C.A., and Allshire, R.C. (2019). Interspecies conservation of organisation and function between nonhomologous regional centromeres. Nat Comms 10, 2343.
Singh, P.P., Shukla, M., White, S.A., Lafos, M., Tong, P., Auchynnikava, T., Spanos, C., Rappsilber, J., Pidoux, A.L., and Allshire, R.C. (2020). Hap2-Ino80-facilitated transcription promotes de novo establishment of CENP-A chromatin. Genes Dev 34, 226–238.
A. Label-free quantitative mass spectrometry detects strong enrichment of all known subunits of inner and outer kinetochore complexes and the Ino80 chromatin remodelling complex in affinity purified CENP-A chromatin.
B. Auxiliary Hap2 Ino80 Complex subunit is required for de novo establishment of CENP-A chromatin on introduced centromere DNA.
C. Transcription from promoters in centromere DNA is reduced in the absence of Hap2.
D. Model. Hap2–Ino80-mediated transcription facilitates de novo establishment of CENP-A chromatin on naïve centromere DNA.