May play a role in transcription or may interact with other nuclear matrix proteins to form the internal fibrogranular network. In association with the SFPQ-NONO heteromer may play a role in nuclear retention of defective RNAs. Plays a role in the regulation of DNA virus-mediated innate immune response by assembling into the HDP-RNP complex, a complex that serves as a platform for IRF3 phosphorylation and subsequent innate immune response activation through the cGAS-STING pathway (PubMed:28712728). Binds to N6-methyladenosine (m6A)-containing mRNAs and contributes to MYC stability by binding to m6A-containing MYC mRNAs (PubMed:32245947). May bind to specific miRNA hairpins (PubMed:28431233). Part of a complex consisting of SFPQ, NONO and MATR3. Interacts with AGO1 and AGO2. Part of a complex composed at least of ASCL2, EMSY, HCFC1, HSPA8, CCAR2, MATR3, MKI67, RBBP5, TUBB2A, WDR5 and ZNF335; this complex may have a histone H3-specific methyltransferase activity. Interacts with TARDBP. Part of the HDP-RNP complex composed of at least HEXIM1, PRKDC, XRCC5, XRCC6, paraspeckle proteins (SFPQ, NONO, PSPC1, RBM14, and MATR3) and NEAT1 RNA (PubMed:28712728). Interacts with FUS. Interacts with IGF2BP1; the interaction is enhanced by SEPIN14P20 peptide RBPR (PubMed:32245947, PubMed:29476152). Interacts with IGF2BP2 and IGF2BP3 (PubMed:29476152). The disease is caused by variants affecting the gene represented in this entry. Extended N-terminus.