A predominantly nuclear protein affecting cytoplasmic localization of beta-actin mRNA in fibroblasts and neurons.
The localization of beta-actin mRNA to the leading lamellae of chicken fibroblasts and neurite growth cones of developing neurons requires a 54-nt localization signal (the zipcode) within the 3' untranslated region. In this study we have identified and isolated five proteins binding to the zipcode. One of these we previously identified as zipcode binding protein (ZBP)1, a 4-KH domain protein. A second is now investigated in detail: a 92-kD protein, ZBP2, that is especially abundant in extracts from embryonic brain. We show that ZBP2 is a homologue of the human hnRNP protein, KSRP, that appears to mediate pre-mRNA splicing. However, ZBP2 has a 47-amino acid (aa) sequence not present in KSRP. Various portions of ZBP2 fused to GFP indicate that the protein most likely shuttles between the nucleus and the cytoplasm, and that the 47-aa insert promotes the nuclear localization. Expression of a truncated ZBP2 inhibits the localization of beta-actin mRNA in both fibroblast and neurons. These data suggest that ZBP2, although predominantly a nuclear protein, has a role in the cytoplasmic localization of beta-actin mRNA.
Gu
Wei
W
Department of Anatomy, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Pan
Feng
F
Zhang
Honglai
H
Bassell
Gary J
GJ
Singer
Robert H
RH
D000199:Actins / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000166:cytology / Q000378:metabolism; D002642:Chick Embryo; D002645:Chickens / Q000235:genetics; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000235:genetics* / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D005347:Fibroblasts / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009474:Neurons / Q000378:metabolism*; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D015534:Trans-Activators
D000199:Actins; D018076:DNA, Complementary; C105789:KHSRP protein, human; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D015534:Trans-Activators; C446510:ZBP2 protein, Gallus gallus