Characterization of transactivation domain and developmental expression of pituitary specific transcription factor, Pit-1 of ayu (Plecoglossus altivelis).
Pit-1 is a pituitary-specific transcription factor, which regulates the expression of growth hormone, prolactin, and thyroid stimulating hormone-beta genes. We previously reported the expression of a Pit-1 gene from ayu (Plecoglossus altivelis), which is an important cultivated food fish in Taiwan and Japan. Comparison of ayu Pit-1 with that of salmon, turkey, and rodent, revealed that the Pit-1 structure is highly conserved through vertebrates, especially in POU-specific and POU-homeo domains. The variation among fish, bird, and mammal are mainly found in transactivation domain by alternative splicing and initiation. Three insertions were found. The gamma-insert in fish Pit-1 is homologous to the exon 2a of avian Pit-1, which is not found in mammals. The beta-insert of fish Pit-1 is homologous to the 28 amino acids (a.a.) and 26 a.a. insert of avian Pit-1 beta(*) and mammalian Pit-1 beta, respectively. An additional similarity was noticed between fish and bird, as both of them contain 7 a.a. insert that is not present in mammalian Pit-1. By site directed mutagenesis, we demonstrated that the beta, gamma, and the 7 a.a. inserts of ayu Pit-1 are critical for activation of zebrafish growth hormone promoter. The ayu Pit-1 protein was found to be expressed specifically in pituitary gland, and its mRNA was first detected at embryonic day 4, significantly increased at embryonic day 5, then sustained to time of hatching at day 8.
Chiu
Chi-Chien
CC
Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan, ROC.
Ting
Jing-Wen
JW
Hseu
Tzong-Hsiung
TH
Chang
Chi-Yao
CY
D016475:3T3 Cells; D017398:Alternative Splicing; D000818:Animals; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000235:genetics*; D015870:Gene Expression; D051379:Mice; D016297:Mutagenesis, Site-Directed; D036441:Osmeriformes / Q000235:genetics* / Q000254:growth & development; D010902:Pituitary Gland / Q000737:chemistry / Q000196:embryology / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000235:genetics*; D015533:Transcriptional Activation / Q000235:genetics*; D014162:Transfection; D015027:Zebrafish / Q000235:genetics
D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; C494185:Pou1f1 protein, mouse