An X-chromosome RNA-binding motif protein (RBMX) is required for proper kinetochore formation

RBMX is an RNA-binding motif protein identified as a component of purified human metaphase chromosomes. We have analyzed the functional significance of RBMX by electron microscopy (EM) in combination with RNA interference (RNAi). We revealed that depletion of RBMX results in the accumulation of mitotic cells. EM investigation further showed that RBMX depletion leads to an increase in the fuzzy ball structure that is reminiscent of the prekinetochore. It is most probably due to the result of disruption at early stages of kinetochore maturation, so that kinetochore differentiation into the authentic trilaminar morphology is disturbed. The present EM data illuminated the importance of RBMX in kinetochore formation for subsequent stable microtubules interaction.