DNA- and RNA-binding protein involved in several cellular processes such as nuclear chromatin organization, telomere-length regulation, transcription, mRNA alternative splicing and stability, Xist-mediated transcriptional silencing and mitotic cell progression (PubMed:10490622, PubMed:18082603, PubMed:19029303, PubMed:22325991, PubMed:25986610, PubMed:28622508). Plays a role in the regulation of interphase large-scale gene-rich chromatin organization through chromatin-associated RNAs (caRNAs) in a transcription-dependent manner, and thereby maintains genomic stability (PubMed:1324173, PubMed:8174554, PubMed:28622508). Required for the localization of the long non-coding Xist RNA on the inactive chromosome X (Xi) and the subsequent initiation and maintenance of X-linked transcriptional gene silencing during X-inactivation (By similarity). Plays a role as a RNA polymerase II (Pol II) holoenzyme transcription regulator (PubMed:8174554, PubMed:9353307, PubMed:10490622, PubMed:15711563, PubMed:19617346, PubMed:23811339). Promotes transcription initiation by direct association with the core-TFIIH basal transcription factor complex for the assembly of a functional pre-initiation complex with Pol II in a actin-dependent manner (PubMed:10490622, PubMed:15711563). Blocks Pol II transcription elongation activity by inhibiting the C-terminal domain (CTD) phosphorylation of Pol II and dissociates from Pol II pre-initiation complex prior to productive transcription elongation (PubMed:10490622). Positively regulates CBX5-induced transcriptional gene silencing and retention of CBX5 in the nucleus (PubMed:19617346). Negatively regulates glucocorticoid-mediated transcriptional activation (PubMed:9353307). Key regulator of transcription initiation and elongation in embryonic stem cells upon leukemia inhibitory factor (LIF) signaling (By similarity). Involved in the long non-coding RNA H19-mediated Pol II transcriptional repression (PubMed:23811339). Participates in the circadian regulation of the core clock component ARNTL/BMAL1 transcription (By similarity). Plays a role in the regulation of telomere length (PubMed:18082603). Plays a role as a global pre-mRNA alternative splicing modulator by regulating U2 small nuclear ribonucleoprotein (snRNP) biogenesis (PubMed:22325991). Plays a role in mRNA stability (PubMed:17174306, PubMed:17289661, PubMed:19029303). Component of the CRD-mediated complex that promotes MYC mRNA stabilization (PubMed:19029303). Enhances the expression of specific genes, such as tumor necrosis factor TNFA, by regulating mRNA stability, possibly through binding to the 3'-untranslated region (UTR) (PubMed:17174306). Plays a role in mitotic cell cycle regulation (PubMed:21242313, PubMed:25986610). Involved in the formation of stable mitotic spindle microtubules (MTs) attachment to kinetochore, spindle organization and chromosome congression (PubMed:21242313). Phosphorylation at Ser-59 by PLK1 is required for chromosome alignement and segregation and progression through mitosis (PubMed:25986610). Contributes also to the targeting of AURKA to mitotic spindle MTs (PubMed:21242313). Binds to double- and single-stranded DNA and RNA, poly(A), poly(C) and poly(G) oligoribonucleotides (PubMed:1628625, PubMed:8068679, PubMed:8174554, PubMed:9204873, PubMed:9405365). Binds to chromatin-associated RNAs (caRNAs) (PubMed:28622508). Associates with chromatin to scaffold/matrix attachment region (S/MAR) elements in a chromatin-associated RNAs (caRNAs)-dependent manner (PubMed:7509195, PubMed:1324173, PubMed:9204873, PubMed:9405365, PubMed:10671544, PubMed:11003645, PubMed:11909954, PubMed:28622508). Binds to the Xist RNA (PubMed:26244333). Binds the long non-coding H19 RNA (PubMed:23811339). Binds to SMN1/2 pre-mRNAs at G/U-rich regions (PubMed:22325991). Binds to small nuclear RNAs (snRNAs) (PubMed:22325991). Binds to the 3'-UTR of TNFA mRNA (PubMed:17174306). Binds (via RNA-binding RGG-box region) to the long non-coding Xist RNA; this binding is direct and bridges the Xist RNA and the inactive chromosome X (Xi) (By similarity). Also negatively regulates embryonic stem cell differentiation upon LIF signaling (By similarity). Required for embryonic development (By similarity). Binds to brown fat long non-coding RNA 1 (Blnc1); facilitates the recruitment of Blnc1 by ZBTB7B required to drive brown and beige fat development and thermogenesis (By similarity). (Microbial infection) Negatively regulates immunodeficiency virus type 1 (HIV-1) replication by preventing the accumulation of viral mRNA transcripts in the cytoplasm. Oligomer (via ATPase domain and RNA-binding RGG-box region); oligomerization occurs upon ATP-binding in a chromatin-associated RNAs (caRNAs)- and transcription-dependent manner and is required for chromatin decompaction (PubMed:28622508). ATP hydrolysis is required to cycle from an oligomeric to monomeric state to compact chromatin (PubMed:28622508). Component of the coding region determinant (CRD)-mediated complex, composed of DHX9, HNRNPU, IGF2BP1, SYNCRIP and YBX1 (PubMed:19029303). Identified in the spliceosome C complex (PubMed:11991638). Identified in a IGF2BP1-dependent mRNP granule complex containing untranslated mRNAs (PubMed:17289661, PubMed:19029303). Associates with heterogeneous nuclear ribonucleoprotein (hnRNP) particles (PubMed:8174554, PubMed:9204873, PubMed:9405365, PubMed:11909954). Associates (via middle region) with the C-terminal domain (CTD) RNA polymerase II (Pol II) holoenzyme; this association occurs in a RNA-independent manner (PubMed:10490622). Associates (via middle region) with the core-TFIIH basal transcription factor complex; this association inhibits the CTD phosphorylation of RNA polymerase II holoenzyme by down-regulating TFIIH kinase activity (PubMed:10490622). Associates with the telomerase holoenzyme complex (PubMed:18082603). Associates with spindle microtubules (MTs) in a TPX2-dependent manner (PubMed:21242313). Interacts (via C-terminus) with actin; this interaction is direct and mediates association with the phosphorylated CTD of RNA polymerase II and is disrupted in presence of the long non-coding H19 RNA (PubMed:15711563, PubMed:23811339). Interacts with AURKA (PubMed:21242313, PubMed:25986610). Interacts (via C-terminus) with CBX5; this interaction is, at least in part, RNA-dependent (PubMed:19617346). Interacts with CR2 (PubMed:7753047). Interacts with CRY1 (By similarity). Interacts (via C-terminus) with EP300; this interaction enhances DNA-binding to nuclear scaffold/matrix attachment region (S/MAR) elements (PubMed:11909954). Interacts with ERBB4 (PubMed:20858735). Interacts with GEMIN5 (PubMed:25911097). Interacts with IGF2BP1 (PubMed:17289661, PubMed:23640942). Interacts with IGF2BP2 and IGF2BP3 (PubMed:23640942). Interacts with NCL; this interaction occurs during mitosis (PubMed:21242313). Interacts (via C-terminus) with NR3C1 (via C-terminus) (PubMed:9353307). Interacts with PLK1; this interaction induces phosphorylation of HNRNPU at Ser-59 in mitosis (PubMed:25986610). Interacts with POU3F4 (PubMed:9105675). Interacts with SMARCA4; this interaction occurs in embryonic stem cells and stimulates global Pol II-mediated transcription. Interacts (via C-terminus) with TOP2A; this interaction protects the topoisomerase TOP2A from degradation and positively regulates the relaxation of supercoiled DNA by TOP2A in a RNA-dependent manner (By similarity). Interacts with TPX2; this interaction recruits HNRNPU to spindle microtubules (MTs) (PubMed:21242313, PubMed:25986610). Interacts with UBQLN2 (PubMed:25616961). Interacts (via RNA-binding RGG-box region) with ZBTB7B; the interaction facilitates the recruitment of long non-coding RNA Blnc1 by ZBTB7B (By similarity). Interacts with ERCC6 (PubMed:26030138). (Microbial infection) Interacts with HIV-1 protein Rev. Localizes at inactive X chromosome (Xi) regions (PubMed:11003645, PubMed:14608463, PubMed:15563465). Localizes in the nucleus during interphase (PubMed:21242313). At metaphase, localizes with mitotic spindle microtubules (MTs) (PubMed:21242313). At anaphase, localizes in the mitotic spindle midzone (PubMed:21242313). Localizes in spindle MTs proximal to spindle poles in a TPX2- and AURKA-dependent manner (PubMed:21242313). The Ser-59 phosphorylated form localizes to centrosomes during prophase and metaphase, to mitotic spindles in anaphase and to the midbody during cytokinesis (PubMed:25986610). Colocalizes with SMARCA4 in the nucleus (By similarity). Colocalizes with CBX5 in the nucleus (PubMed:19617346). Colocalizes with NR3C1 in nuclear speckles (PubMed:9353307). Localized in cytoplasmic ribonucleoprotein (RNP) granules containing untranslated mRNAs (PubMed:17289661). Widely expressed. The SAP domain is necessary for specific binding to nuclear scaffold/matrix attachment region (S/MAR) elements in DNA (PubMed:9405365, PubMed:11003645). The RNA-binding RGG-box region is necessary for its association with inactive X chromosome (Xi) regions and to chromatin-associated RNAs (caRNAs) (PubMed:14608463, PubMed:28622508). Both the DNA-binding domain SAP and the RNA-binding RGG-box region are necessary for the localization of Xist RNA on the Xi (By similarity). The ATPase and RNA-binding RGG-box regions are necessary for oligomerization (PubMed:28622508). Cleaved at Asp-100 by CASP3 during T-cell apoptosis, resulting in a loss of DNA- and chromatin-binding activities (PubMed:9405365, PubMed:10671544). Extensively phosphorylated (PubMed:7993898). Phosphorylated on Ser-59 by PLK1 and dephosphorylated by protein phosphatase 2A (PP2A) in mitosis (PubMed:25986610). Arg-739 is dimethylated, probably to asymmetric dimethylarginine (Ref.8). Arg-733 is dimethylated, probably to asymmetric dimethylarginine (By similarity). Citrullinated by PADI4. The disease is caused by variants affecting the gene represented in this entry. Aberrant splicing.