Squid hnRNP protein promotes apical cytoplasmic transport and localization of Drosophila pair-rule transcripts.
Drosophila melanogaster pair-rule segmentation gene transcripts localize apically of nuclei in blastoderm embryos. This might occur by asymmetric (vectorial) export from one side of the nucleus or by transport within the cytoplasm. We have followed fluorescently labeled pair-rule transcripts postinjection into Drosophila embryos. Naked, microinjected fushi tarazu (ftz) transcripts do not localize in blastoderm embryos, indicating that cytoplasmic mechanisms alone are insufficient for apical targeting. However, prior exposure of ftz to Drosophila or human embryonic nuclear extract leads to rapid, specific, microtubule-dependent transport, arguing against vectorial export. We present evidence that ftz transcript localization involves the Squid (Hrp40) hnRNP protein and that the activity of hnRNP proteins in promoting transcript localization is evolutionarily conserved. We propose that cytoplasmic localization machineries recognize transcripts in the context of nuclear partner proteins.
Lall
S
S
Developmental Genetics Laboratory, Imperial Cancer Research Fund, London, United Kingdom.
Francis-Lang
H
H
Flament
A
A
Norvell
A
A
Schüpbach
T
T
Ish-Horowicz
D
D
D020413:3' Untranslated Regions / Q000502:physiology; D008841:Actin Cytoskeleton / Q000502:physiology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D001756:Blastoderm / Q000378:metabolism; D003432:Cross-Linking Reagents; D003593:Cytoplasm / Q000378:metabolism; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics* / Q000254:growth & development; D004625:Embryo, Nonmammalian / Q000378:metabolism; D019143:Evolution, Molecular; D005260:Female; D051717:Fushi Tarazu Transcription Factors; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D007301:Insect Hormones / Q000378:metabolism*; D008845:Microinjections; D008870:Microtubules / Q000502:physiology; D009687:Nuclear Proteins / Q000494:pharmacology; D010053:Ovary / Q000737:chemistry; D011485:Protein Binding / Q000502:physiology; D012333:RNA, Messenger / Q000493:pharmacokinetics; D016601:RNA-Binding Proteins / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology; D014466:Ultraviolet Rays
D020413:3' Untranslated Regions; D003432:Cross-Linking Reagents; D029721:Drosophila Proteins; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; D007301:Insect Hormones; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C497169:ftz protein, Drosophila; C081480:sqd protein, Drosophila