M-specific activator (MSA) cis-acting elements have been determined to be involved in the regulation of G2/M-phase-specific transcription in spermatophytes. In this study, the involvement of MSA-core elements in G2/M-phase-specific transcription was examined in the unicellular red alga Cyanidioschyzon merolae. In the C. merolae genome, MSA-core elements do not accumulate specifically in the upstream of mitosis-specific transcriptional genes. Mutations of the four MSA-core elements of the cyclin B gene, which encodes a central factor of the G2-to-M-phase transition, have resulted in the abolishment of transcription or permission of transcription even in the G1 phase. These results suggest that all four MSA-core elements located in the upstream region of cyclin B are involved in G2/M-phase-specific transcription in C. merolae; however, the nature of the involvement of MSA-core elements in G2/M-phase-specific transcription differed among the four elements. Thus, MSA-core-element-mediated G2/M-phase-specific transcription in C. merolae seems to be regulated by a complex mechanism.

已确定M 特异性激活因子 (MSA)顺式作用元件参与调节精子植物中 G2/M 期特异性转录。在这项研究中，在单细胞红藻Cyanidioschyzon merolae中检查了 MSA 核心元件在 G2/M 期特异性转录中的参与。在C. merolae基因组中，MSA 核心元件不会在有丝分裂特异性转录基因的上游特异性积累。细胞周期蛋白 B的四个 MSA 核心元件的突变编码 G2 到 M 期转变的中心因子的基因即使在 G1 期也导致转录的取消或转录的允许。这些结果表明，位于细胞周期蛋白B上游区域的所有四个MSA核心元件都参与了C. merolae的G2/M期特异性转录；然而，MSA 核心元件参与 G2/M 期特异性转录的性质在四种元件之间有所不同。因此， C. merolae中 MSA 核心元件介导的 G2/M 期特异性转录似乎受到复杂机制的调节。