State Key Laboratory of Microbial Technology, School of Life Science, Shandong University, Jinan, Shandong, China.
Curr Microbiol. 2013 Nov;67(5):580-9. doi: 10.1007/s00284-013-0396-4. Epub 2013 Jun 9.
Gcn5 is a well-established histone acetyltransferase involved in chromatin modification by catalyzing the acetylation of specific lysine residues within the N-terminal tails of the core histones. To assess the role of chromatin remodeling in the transcriptional response of cellulolytic Trichoderma reesei to the changes of environmental conditions, we identified the T. reesei ortholog of Saccharomyces cerevisiae Gcn5 by sequence alignment and functional analysis. Heterologous expression of TrGcn5 in S. cerevisiae gcn5Δ strain restored the growth defect under nutrient limitation as well as stresses. In contrast, mutant TrGcn5 with site-directed changes of residues critical for Gcn5 histone acetyltransferase activity could not complement the growth defect. The T. reesei gcn5Δ mutant strain displayed a strongly decreased growth rate and dramatic morphological changes including misshapen hyphal cells and abolished conidiation. Moreover, the induced expression of cellulase genes was severely impaired in the gcn5Δ T. reesei with acetylation of K9 and K14 of histone H3 in the cellulase gene promoter dramatically affected in the absence of TrGcn5. The results indicate that TrGcn5 plays a critical role in filamentous growth, morphogenesis, and transcriptional activation of specific genes including cellulase encoding genes.
Gcn5 是一种经过充分验证的组蛋白乙酰转移酶，通过催化核心组蛋白 N 端尾部特定赖氨酸残基的乙酰化作用，参与染色质修饰。为了评估染色质重塑在纤维素分解真菌里氏木霉对环境条件变化的转录反应中的作用，我们通过序列比对和功能分析，鉴定了里氏木霉与酿酒酵母 Gcn5 的直系同源物。在酿酒酵母 gcn5Δ 菌株中异源表达 TrGcn5 可以恢复营养限制以及应激条件下的生长缺陷。相比之下，突变 TrGcn5 中关键残基的定点改变，这些残基对于 Gcn5 组蛋白乙酰转移酶活性至关重要，不能弥补生长缺陷。gcn5Δ 突变株的里氏木霉生长速度明显降低，形态发生剧烈变化，包括菌丝细胞畸形和分生孢子形成完全丧失。此外，在 gcn5Δ T. reesei 中，纤维素酶基因的诱导表达受到严重损害，组蛋白 H3 的 K9 和 K14 乙酰化作用在没有 TrGcn5 的情况下对纤维素酶基因启动子产生了显著影响。结果表明，TrGcn5 在丝状生长、形态发生和特定基因（包括纤维素酶编码基因）的转录激活中发挥着关键作用。
