ASPA and AceCS1 nuclear co-localization is regulated during cell cycle progression.

A) ASPA immunoreactivity was examined in the absence or presence of 0.25% GTA for 1, 3, or 5, days (2, 4, 6 days in vitro). In stem cell medium (on PLL-coated dish), OG33 cells grew as small adherent clusters while OG35 cells displayed a more splayed morphology. In both cases, ASPA was comparably expressed in the cytosol and nucleus. In differentiation medium, ASPA immunoreactivity was particularly enriched within the nucleus, and GTA reduced ASPA expression. B) Subcellular fractionation revealed that ASPA was more abundant in the cytosol (C), than nucleus (N), of both OG cell cultured in DM with 10 μM NAAG for 4 days. The lower molecular weight Aspa species induced by increased acetate bioavailability (by GTA, Figure 4A, and NAAG, shown here) exclusively partitioned to the nucleus. C) ASPA and AceCS1 were co-localized in the nucleus of untreated OG33 and OG35 cells cultured in DM for 3 days (4 days in vitro). Co-localization is most pronounced during metaphase (arrows). D) ASPA spatial localization in the nucleus of OG33 cells cultured in DM for 3 days (4 days in vitro) was present surrounding the metaphase equatorial plate and aligned chromosomes (DAPI staining, large single arrows). As sister chromatids separated in anaphase, ASPA immunoreactivity became more diffuse (small double arrows). Scale bar = 100 μm (A), 50 μm (C, D).