Characterization of transactivation domain and developmental expression of pituitary specific transcription factor, Pit-1 of ayu ( Plecoglossus altivelis)

• Published in: General and comparative endocrinology 2002-07, Vol.127 (3), p.307-313
• Main Authors: Chiu, Chi-Chien, Ting, Jing-Wen, Hseu, Tzong-Hsiung, Chang, Chi-Yao
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Alternative Splicing; Animals; Ayu; Conserved Sequence; Development; DNA-Binding Proteins - genetics; Gene Expression; Mice; Mutagenesis, Site-Directed; Osmeriformes - genetics; Osmeriformes - growth & development; Pit-1; Pituitary; Pituitary Gland - chemistry; Pituitary Gland - embryology; Pituitary Gland - metabolism; Promoter Regions, Genetic; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - analysis; Transcription factor; Transcription Factor Pit-1; Transcription Factors - genetics; Transcriptional Activation - genetics; Transfection; Zebrafish - genetics
• ISSN: 0016-6480; 1095-6840
• DOI: 10.1016/S0016-6480(02)00057-6

Pit-1 is a pituitary-specific transcription factor, which regulates the expression of growth hormone, prolactin, and thyroid stimulating hormone-β 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 γ-insert in fish Pit-1 is homologous to the exon 2a of avian Pit-1, which is not found in mammals. The β-insert of fish Pit-1 is homologous to the 28 amino acids (a.a.) and 26 a.a. insert of avian Pit- 1 β ∗ and mammalian Pit-1β, 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 β, γ, 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.