During anaphase, BUB-1 remains at the core of the ring domains, while AIR-2 concentrates more around the edges of the rod-like structures, closer to chromosomes (Fig.?2A, yellow arrows). show that CLS-2 is usually subject to SUMO-mediated regulation; CLS-2 precociously localises in the midbivalent when either SUMO or GEI-17 are depleted. Overall, we provide evidence for any novel, VAV3 SUMO-mediated control of protein dynamics during early anaphase I in oocytes. contains holocentric chromosomes (Maddox et al., 2004) and has served as an extremely useful system to uncover ATN-161 mechanisms of meiosis and mitosis for almost 20 years (Oegema et al., 2001; Desai et al., 2003; Cheeseman et al., 2004, 2005; Monen et al., 2005). Meiosis is a specialised cell division with two successive rounds of chromosome segregation that reduce the ploidy and generates haploid gametes (Ohkura, 2015; Duro and Marston, 2015; Severson et al., 2016). During meiosis I, homologous chromosomes segregate while sister chromatid cohesion is usually managed. During meiosis II, sister chromatid cohesion is usually lost, reminiscent of mitotic chromosome segregation (Dumont and Desai, 2012; Duro and Marston, 2015; Bennabi et al., 2016; Severson et al., 2016). During female meiosis, kinetochores disassemble in early anaphase I and appear to be dispensable for chromosome segregation (Dumont et al., 2010; Hattersley et al., 2016; McNally et ATN-161 al., 2016). In addition, tomographic reconstruction in electron microscopy of the female meiotic spindle has revealed that, during anaphase I, central spindle MTs transition from a lateral to an end-on orientation (Laband et al., 2017; Redemann et al., 2018; Yu et al., 2019 preprint). Therefore, while the balance between central spindle MT- and kMT-driven causes may vary in different spindles, the former seems most important during female meiosis in oocytes. During early anaphase, the midbivalent rings stretch into rod-like structures within the central spindle, and SUMO remains strongly concentrated in these structures (Fig.?1A). High-resolution live imaging of dissected oocytes expressing GFP-tagged SUMO shows that the SUMO transmission increases after anaphase onset, peaking during early anaphase (Fig.?1A,B; Movie?1). This is followed by a diffusion throughout the central spindle and a sharp decrease in intensity at 100?s after anaphase onset (Fig.?1A,B). We have shown before that GEI-17, the sole PIAS orthologue, is the important meiotic SUMO E3 ligase (Pelisch et al., 2017). The SUMO E3 ligase GEI-17 displays a similar localisation pattern to that of SUMO, supporting the notion that SUMO conjugation is usually actively taking place during early anaphase (Fig.?1C,D). To assess the role of SUMO during anaphase I progression, we investigated the localisation and role of two proteins shown to play important functions during meiotic chromosome segregation: BUB-1 and Air flow-2 (Dumont et al., 2010; Kaitna et al., 2002; Rogers et al., 2002; Muscat et al., 2015; Laband et al., 2017). Air flow-2 concentrates in the midbivalent ring domain name (Kaitna et al., 2002; Rogers et al., 2002), while BUB-1 is present in the ring domain and also in kinetochores (Monen et al., 2005; Dumont et al., 2010; Laband et al., 2017). In agreement with this, we observed a strong Air flow-2 and BUB-1 colocalisation in the midbivalent ring (Fig.?2A, cyan arrows). During anaphase, BUB-1 remains at the core of the ring domains, while Air flow-2 concentrates more on the edges of the rod-like structures, closer to chromosomes (Fig.?2A, yellow arrows). Later in anaphase (as judged by the chromosome separation), Air flow-2 and BUB-1 occupy completely non-overlapping domains within segregating chromosomes (Fig.?2A, 2.5?m). During late anaphase, the BUB-1 transmission is usually lost altogether while Air flow-2 concentrates solely in the central spindle, where MTs (not shown in the physique) have populated the entire area (Fig.?2A, 3.5?m). Such Air flow-2 and BUB-1 dynamic localisations were confirmed by live imaging of dissected oocytes. During early anaphase, both BUB-1 and ATN-161 Air flow-2 localise predominantly in rod-like structures (Fig.?2B). Additionally, two other CPC components, ICP-1 and BIR-1 display a similar localisation to Air flow-2 (Fig.?S1). The strong BUB-1CAIR-2 colocalisation occurs during metaphase and early anaphase (Fig.?2B), coinciding with the peak in SUMO conjugation. We then compared SUMO localisation to that of BUB-1 and Air flow-2 in live oocytes. SUMO colocalises with Air flow-2 during metaphase and early anaphase (Fig.?S2). BUB-1 and SUMO colocalise in the ring domain name, but no SUMO is usually detected in kinetochores during metaphase I (Fig.?2C; Movie?2). As anaphase progresses and kinetochores disassemble, ATN-161 the BUB-1 kinetochore transmission disappears and concentrates in the stretched ring domains, as shown in fixed samples. At this stage, BUB-1 and SUMO display identical localisation patterns (Fig.?2C; Movie?2). During late anaphase, BUB-1 and SUMO not only display identical localisation but also both proteins become diffuse as they also decrease in intensity, until both proteins.