Nuclear actin is associated with a specific subset of hnRNP A/B-type proteins

• Published in: Nucleic acids research Vol. 30; no. 8; pp. 1725 - 1734
• Main Authors: Percipalle, Piergiorgio, Jonsson, Andreas, Nashchekin, Dmitri, Karlsson, Christina, Bergman, Tomas, Guialis, Apostolia, Daneholt, Bertil
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 15.04.2002; Oxford Publishing Limited (England)
• Subjects: Actins - metabolism; Active Transport, Cell Nucleus; Amino Acid Sequence; Animals; CBF-A protein; Cell Nucleus - metabolism; COS Cells; DBP40 protein; Electrophoresis, Gel, Two-Dimensional; Heterogeneous-Nuclear Ribonucleoprotein Group A-B; Heterogeneous-Nuclear Ribonucleoproteins; hnRNP A/B protein; Mass Spectrometry; Medicin och hälsovetenskap; Microscopy, Fluorescence; Molecular Sequence Data; Rats; Ribonucleoproteins - chemistry; Ribonucleoproteins - metabolism; RNA Precursors - metabolism; RNA, Messenger - metabolism
• ISSN: 0305-1048; 1362-4962; 1362-4962
• DOI: 10.1093/nar/30.8.1725

Pre-mRNP complexes were isolated from rat liver nuclei as 40S hnRNP particles, and actin-binding proteins were collected by DNase I affinity chromatography. The bound proteins were analyzed by 2D gel electrophoresis, and the following five hnRNP A/B-type proteins were identified by tandem mass spectrometry: DBP40/CBF-A (CArG binding factor A), a minor hnRNP A2 variant and three minor hnRNP A3 (mBx) variants. DBP40 was chosen for further analysis of the association of actin with the pre-mRNP complex. It was shown in vitro that purified actin binds to recombinant DBP40 suggesting that the interaction between actin and DBP40 is direct in the pre-mRNP particles. The association of actin with DBP40 was further explored in vivo. It was shown in a transfection study that DBP40 appears both in the nucleus and cytoplasm. Microinjection experiments revealed that DBP40 is exported from the nucleus to the cytoplasm. Finally, RNA–protein and protein–protein cross-linking experiments showed that DBP40 interacts with poly(A)+ RNA as well as actin, both in the nucleus and cytoplasm. We propose that actin associated with DBP40, and perhaps with additional hnRNP A/B-type proteins, is transferred from nucleus to cytoplasm bound to mRNA.