The function of MCRS1 (microspherule protein 1, ENSG00000187778) is as follows. Modulates the transcription repressor activity of DAXX by recruiting it to the nucleolus (PubMed:11948183). As part of the NSL complex, may be involved in acetylation of nucleosomal histone H4 on several lysine residues (PubMed:20018852). Putative regulatory component of the chromatin remodeling INO80 complex which is involved in transcriptional regulation, DNA replication and probably DNA repair. May also be an inhibitor of TERT telomerase activity (PubMed:15044100). Binds to G-quadruplex structures in mRNA (PubMed:16571602). Binds to RNA homomer poly(G) and poly(U) (PubMed:16571602). Maintains RHEB at the lysosome in its active GTP-bound form and prevents its interaction with the mTORC1 complex inhibitor TSC2, ensuring activation of the mTORC1 complex by RHEB (PubMed:25816988). Stabilizes the minus ends of kinetochore fibers by protecting them from depolymerization, ensuring functional spindle assembly during mitosis (PubMed:22081094, PubMed:27192185). Following phosphorylation by TTK/MPS1, enhances recruitment of KIF2A to the minus ends of mitotic spindle microtubules which promotes chromosome alignment (PubMed:30785839). Regulates the morphology of microtubule minus ends in mitotic spindle by maintaining them in a closed conformation characterized by the presence of an electron-dense cap (PubMed:36350698). Regulates G2/M transition and spindle assembly during oocyte meiosis (By similarity). Mediates histone modifications and transcriptional regulation in germinal vesicle oocytes which are required for meiotic progression (By similarity). Also regulates microtubule nucleation and spindle assembly by activating aurora kinases during oocyte meiosis (By similarity). Contributes to the establishment of centriolar satellites and also plays a role in primary cilium formation by recruiting TTBK2 to the mother centriole which is necessary for removal of the CP110 cap from the mother centriole, an early step in ciliogenesis (PubMed:27263857). Required for epiblast development during early embryogenesis (By similarity). Essential for cell viability (PubMed:16547491). {ECO:0000250|UniProtKB:Q99L90, ECO:0000269|PubMed:11948183, ECO:0000269|PubMed:15044100, ECO:0000269|PubMed:16547491, ECO:0000269|PubMed:16571602, ECO:0000269|PubMed:20018852, ECO:0000269|PubMed:22081094, ECO:0000269|PubMed:25816988, ECO:0000269|PubMed:27192185, ECO:0000269|PubMed:27263857, ECO:0000269|PubMed:30785839, ECO:0000269|PubMed:36350698}.