Aurora-B/AIM-1 Regulates the Dynamic Behavior of HP1α at the G₂–M Transition

Abstract

Heterochromatin protein 1 (HP1) plays an important role in heterochromatin formation and undergoes large-scale, progressive dissociation from heterochromatin in prophase cells. However, the mechanisms regulating the dynamic behavior of HP1 are poorly understood. In this study, the role of Aurora-B was investigated with respect to the dynamic behavior of HP1␣. Mammalian Aurora-B, AIM-1, colocalizes with HP1␣ to the heterochromatin in G 2 . Depletion of Aurora-B/AIM-1 inhibited dissociation of HP1␣ from the chromosome arms at the G 2 -M transition. In addition, depletion of INCENP led to aberrant cellular localization of Aurora-B/AIM-1, but it did not affect heterochromatin targeting of HP1␣. It was proposed in the binary switch hypothesis that phosphorylation of histone H3 at Ser-10 negatively regulates the binding of HP1␣ to the adjacent methylated Lys-9. However, Aurora-B/AIM-1-mediated phosphorylation of H3 induced dissociation of the HP1␣ chromodomain but not of the intact protein in vitro, indicating that the center and/or C-terminal domain of HP1␣ interferes with the effect of H3 phosphorylation on HP1␣ dissociation. Interestingly, Lys-9 methyltransferase SUV39H1 is abnormally localized together along the metaphase chromosome arms in Aurora-B/AIM-1-depleted cells. In conclusion, these results showed that Aurora-B/AIM-1 is necessary for regulated histone modifications involved in binding of HP1␣ by the N terminus of histone H3 during mitosis. INTRODUCTIONChromosomal passenger proteins are characterized by the unique property of translocation from the chromosome to the central spindle at the onset of anaphase (reviewed in Adams et al., 2001a;Terada 2001). In G 2 and prophase, chromosomal passengers are localized on the chromosome, whereas during prometaphase and metaphase they translocate to the inner centromeres. During anaphase the chromosomal passengers transfer to the spindle midzone where they eventually become part of the midbody (Earnshaw and Cooke, 1991). At the onset of anaphase, separase cleaves the cohesin protein into separate sister chromatids and activates at the same time the phosphatase Cdc14, which dephosphorylates Inner Centromere Protein (INCENP) and triggers its relocalization to the spindle midzone (Pereira and Schiebel, 2003). Recent results show that Aurora-B, together with INCENP and Survivin/BIR, is part of a chromosomal passenger complex. Aurora-B binds to Survivin and the Cterminal domain of INCENP (reviewed in Adams et al., 2001b;Terada 2001). It is of particular interest that all metazoan INCENPs as well as the INCENP homologue of Saccharomyces cerevisiae (Sli5p) share a highly conserved motif near the C terminus, the so-called IN-box (INCENP conserved box) (Adams et al., 2000), which is required for interaction with Aurora-B. Disruption of Aurora-B, INCENP, or Survivin/BIR function leads in several species to severe defects in chromosome segregation and cytokinesis , Giet and Glover, 2001. In Drosophila cells and. elegans embryos that lack INCENP or Survivin, Aurora-B cannot prop...

cAMP signaling induces rapid loss of histone H3 phosphorylation in mammary adenocarcinoma-derived cell lines

“…Thus, a global loss of serine 10 phosphorylation would be predicted to lead to an increase in lysine 9 methylation in areas of chromatin where SUV39H1 is localized. In support, inhibition of mitotic H3 phosphorylation at serine 10 by knockdown of Aurora B kinase expression has been shown to result in increased association of SUV39H1 with mitotic chromosomes [29]. This study further supports a reciprocal relationship between serine 10 phosphorylation and lysine 9 methylation in vivo.…”

Dynamic Regulation of Effector Protein Binding to Histone Modifications: The Biology of HP1 Switching

“…55 Second, and in contrast to earlier in vitro findings, 56 mass spectrometric and immunological approaches unambiguously identified the K9me and S10ph marks present on the same histone H3 tail at the beginning of M-phase (Fig. 2B).…”

“…57,58 In vitro phosphorylation by this kinase complex is sufficient to interrupt the interaction of the different HP1 chromo domains with a H3K9me3 peptide. 53 In agreement with a crucial role of H3S10 phosphorylation in the mitotic release of HP1 proteins from chromatin, depletion of Aurora B by RNA interference or antibodies, [53][54][55] inhibition of enzymatic Aurora B activity with the small molecule inhibitor hesperadin, 53,54,59 or overexpression of a H3 mutant that cannot be phosphorylated at serine 10 (H3S10A) 55 all result in retention of the effectors on chromosome arms.…”

“…47,49,50 While dissociation of almost all of HP1 from chromatin is observed, most surprisingly its binding site, H3K9me3, persists during M-phase. [51][52][53] Results presented in several recently published studies [53][54][55] have shed light on this paradoxical interruption of the signaling axis HP1-H3K9me3.…”

“…53,54 Indeed, in in vitro binding studies, HP1 interaction with a dually, K9me3S10ph-modified H3 peptide is much weaker compared to a singly, K9me3-modified H3 tail. [53][54][55] The kinase responsible for mitotic phosphorylation of H3S10 is Aurora B, a component of the chromosomal passenger complex (CPC). 57,58 In vitro phosphorylation by this kinase complex is sufficient to interrupt the interaction of the different HP1 chromo domains with a H3K9me3 peptide.…”