Characterization of Heat Shock Protein 90B (HSP90B) gene and its promoter in the unicellular green ALGA Chlamydomonas Reinhardtii

• Main Author: Somchoke Traewachiwiphak
• Other Authors: Kittisak Yokthongwattana
• Language: English
• Published: Mahidol University. Mahidol University Library and Knowledge Center 2023
• Subjects: Chlamydomonas reinhardtii; Genes > Analysis; Heat shock proteins
• Online Access: https://repository.li.mahidol.ac.th/handle/123456789/89824
• Institution: Mahidol University

The heat shock proteins (HSPs) are proteins that play important roles in cellular protein homeostasis. There are six classified groups of the HSP proteins: HSP100/Clp, HSP90, HSP70, HSP60/chaperonin, small heat-shock proteins, and calnexin/calreticulin. Due to relatively scarce information at the gene regulation level in the literature, HSP90 family was the subject of interest in this study. In the unicellular green alga Chlamydomonas reinhardtii, there are three HSP90 genes: HSP90A, HSP90B, and HSP90C. Among the three, HSP90B is the least studied, especially in photosynthetic organisms. In this dissertation, the attempt was made to characterize the HSP90B gene as well as the promoter sequence in the model alga C. reinhardtii. I found that the HSP90B genome contained 13 exons and 12 introns encoding for ER-localized protein of 819 amino acids. The HSP90B expression was strongly induced by heat while short-term exposure to other abiotic stresses, such as salinity, or light stress did not appear to affect the expression. Promoter truncation analysis revealed a core constitutive promoter sequence between -1 to -387 bp from the ATG site. Promoter sequence analyses along with ChIP assay followed by qPCR and DNA-protein pull-down assay suggested that the sequence upstream of the core promoter contained repressive elements including sequences with high histone-binding preference as well as putative repressor binding site(s).