Detection, characterization and expression dynamics of histone proteins in the dinoflagellate Alexandrium pacificum during growth regulation

• Published in: Harmful algae Vol. 87; p. 101630
• Main Authors: Riaz, Sadaf, Niaz, Zeeshan, Khan, Sohrab, Liu, Yuan, Sui, Zhenghong
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.07.2019
• Subjects: Amino Acid Sequence; Cell cycle; Dinoflagellate; Dinoflagellida; DNA; Histone expression; Histone genes; Histones; Immune-detection; Mass spectrometry; Phylogeny; Histone genes; Histone expression; Mass spectrometry; Dinoflagellate; Immune-detection; Cell cycle
• ISSN: 1568-9883; 1878-1470
• DOI: 10.1016/j.hal.2019.101630

•Phylogenetic grouping identifies at least two major variants of all histone sequences within A. pacificum•A. pacificum maintains an active transcription of histone genes within cell.•Histones of A. pacificum appear to have a limited role in DNA packaging.•Differential expression of histone transcripts and protein under nutritionally enhanced conditions suggests their functional significance in dinoflagellates.•Histone-like protein is identified as most abundant acid-soluble protein of the cells. Histones are the most abundant proteins associated with eukaryotic nuclear DNA. The exception is dinoflagellates, which have histone protein expression that is mostly reported to be below detectable levels. In this study, we investigated the presence of histone proteins and their functions in the dinoflagellate, Alexandrium pacificum. Histone protein sequences were analyzed, focusing on phylogenetic analysis and histone code. Histone expression was analyzed during the cell cycle and under nutritionally enhanced conditions using quantitative-PCR and western blots. Acid-soluble proteins were subjected to mass spectrometry analysis. To our knowledge, this is the first report of immunological detection of histone proteins (H2B and H4) in any dinoflagellate species. Absolute quantification of histone transcript in activily dividing cells revealed significant transcription in cells. The stable expression of histones during the cell cycle suggested that the histone genes in A. pacificum belonged to a replication-independent class and appeared to have a limited role in DNA packaging. The conservation of numerous post-translationally modified residues of multiple histone variants and differential expression of histones under nutritionally enhanced conditions suggested their functional significance in dinoflagellates. However, we detected histone H2B protein only via mass spectrometry. Histone-like protein was identified as most abundant acid-soluble protein of the cells.