Microspherule protein 1 (MCRS1 or MSP58) is an RNA-binding protein that interacts with Daxx transcriptional regulator, relieving its repressor activity. Overexpression of MCRS1 leads to translocation of Daxx to the enlarged nucleoli in COS-1 or 293 cells []. It also interacts with fragile X messenger ribonucleoprotein 1 (FMRP), which represses specific mRNAs being transported as silent ribonucleoparticles from the cell body of a neuron to the distant synapse. MCRS1 binds to the G-quadruplex structures of the mRNA []. MCRS1 is a component of the NSL complex [], the MLL1/MLL complex [], and is a putative regulatory component in the chromatin remodeling INO80 complex []. The isoform MCRS2 is a cell-cycle-dependent protein which accumulates in the early S phase, and interacts with the telomerase-inhibitory protein LPTS/PinX1 [].
