Developmentally regulated synthesis of p8, a stress-associated transcription cofactor, in diapause-destined embryos of Artemia franciscana.
Diapause-destined embryos of the crustacean Artemia franciscana arrest as gastrulae, acquire extreme stress tolerance, and enter profound metabolic dormancy. Among genes upregulated at 2 days postfertilization in these embryos is a homologue of p8, a stress-inducible transcription cofactor. Artemia p8 is smaller than vertebrate homologues but shares a basic helix-loop-helix domain and a bipartite nuclear localization signal. Probing of restriction digested DNA on Southern blots indicated a single Artemia p8 gene and 5'-RACE specified 2 transcription start sites. Several putative cis-acting regulatory sequences, including two heat shock elements, appeared upstream of the p8 transcription start site. Artemia p8 mRNA increased sharply at 1 day postfertilization in diapause-destined embryos and then declined, whereas p8 protein appeared 2 days postfertilization and remained relatively constant throughout development, indicating a stable protein. p8 was not detectable in nauplius-destined (nondiapause) Artemia embryos. Immunofluorescent staining revealed p8 within Artemia nuclei. The results support the idea that p8, a known stressresponsive transcription cofactor, mediates gene expression in diapause-destined Artemia embryos. p8 is the first diapause-related transcription factor identified in crustaceans and 1 of only a small number of such proteins identified in any organism undergoing diapause.
Qiu
Zhijun
Z
Department of Biology, Dalhousie University, Halifax, NS B3H 4J1, Canada.
MacRae
Thomas H
TH
D000222:Adaptation, Physiological / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001156:Artemia / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000737:chemistry; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013312:Stress, Physiological / Q000196:embryology / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D013997:Time Factors
D051792:Basic Helix-Loop-Helix Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; C491643:NUPR1 protein, human