POLR3A and proteostasis deficiencies: Alternatively, it is thought that mutations of RNA polymerase III subunit A (POLR3A) or RNA polymerase III subunit B (POLR3B) may induce aggregation of POLR3A and POLR3B proteins, leading to proteopathies (also called proteinopathies) associated with gain of function in POLR3A or POLR3B mutants.