Phosphorylation of H3-Thr3 by Haspin Is Required for Primary Cilia Regulation

Abstract

Primary cilia are commonly found on most quiescent, terminally differentiated cells and play a major role in the regulation of the cell cycle, cell motility, sensing, and cell–cell communication. Alterations in ciliogenesis and cilia maintenance are causative of several human diseases, collectively known as ciliopathies. A key determinant of primary cilia is the histone deacetylase HDAC6, which regulates their length and resorption and whose distribution is regulated by the death inducer-obliterator 3 (Dido3). Here, we report that the atypical protein kinase Haspin is a key regulator of cilia dynamics. Cells defective in Haspin activity exhibit longer primary cilia and a strong delay in cilia resorption upon cell cycle reentry. We show that Haspin is active in quiescent cells, where it phosphorylates threonine 3 of histone H3, a known mitotic Haspin substrate. Forcing Dido3 detachment from the chromatin prevents Haspin inhibition from impacting cilia dynamics, suggesting that Haspin activity is required for the relocalization of Dido3–HDAC6 to the basal body. Exploiting the zebrafish model, we confirmed the physiological relevance of this mechanism. Our observations shed light on a novel player, Haspin, in the mechanisms that govern the determination of cilia length and the homeostasis of mature cilia.

Dissecting the roles of Haspin and VRK1 in histone H3 phosphorylation during mitosis

“…A number of H3S10 kinases that act to regulate transcription in interphase cells have been characterized, including MSK1/2 28 , 33 . It is possible that Haspin itself has functions outside mitosis 75 , 92 , and the plant-specific MUT9 kinases generate H3T3ph in Chlamydomonas and Arabidopsis and appear to be involved in epigenetic silencing 93 , 94 . Interestingly, like the VRK family, MUT9 kinases are part of the CK1 superfamily and it is conceivable that VRKs serve a similar function in metazoa.…”

Release of Histone H3K4-reading transcription factors from chromosomes in mitosis is independent of adjacent H3 phosphorylation

“…Notably, methyl-phos switching requires that methylation and phosphorylation co-occur in vivo , but little is known about the precise genome-wide localization of histone phosphorylation in mitosis. Previous studies provided some evidence for H3T3/K4 switching in cells (Ali et al, 2013; Gatchalian et al, 2013; Gatchalian et al, 2016; Noh et al, 2015; Quadri et al, 2021; Varier et al, 2010), but often rely on the inverse correlation of H3T3ph and H3K4 reader protein levels on chromatin in microscopy experiments. Here, we analyze the genome-wide distribution and function of H3T3ph and find that the release of H3K4-reading transcription factors from chromosomes in mitosis is independent of methyl-phos switching.…”