The perinucleolar compartment (PNC) is a subnuclear structure associated with, but structurally distinct from, the nucleolus. The PNC contains large amounts of the heterogeneous nuclear ribonucleoprotein complex (hnRNP) called hnRNP 1 (PTB). Many RNA binding proteins as well as RNA polymerase III transcripts are highly enriched in this compartment. PTB and pol III transcripts are required for the integrity of the PNC.