Houghton-Larsen Jens, Brandt Anders
Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-2500 Copenhagen Valby, Denmark.
Appl Environ Microbiol. 2006 Nov;72(11):7176-82. doi: 10.1128/AEM.01704-06. Epub 2006 Sep 15.
In Saccharomyces cerevisiae, genes encoding maltose permeases and maltases are located in the telomeric regions of different chromosomes. The COMPASS methylation complex, which methylates lysine 4 on histone H3, controls the silencing of telomeric regions. Yeast strains deleted for SWD1, SWD3, SDC1, SET1, BRE2, or SPP1, encoding components of the COMPASS complex, fermented a medium containing 22% maltose with noticeably higher attenuation than did the wild type, resulting in production of up to 29% more ethanol. The least effective strain was spp1. Absence of COMPASS components had no effect on the fermentation of media with 20% glucose, 20% sucrose, or 16% maltose. Deletion of SWD3 resulted in larger amounts of MAL12 transcript, encoding maltase, at the late stages of fermentation of 22% maltose. A similar effect on maltase activity and maltose uptake capability was seen. The lysine 4 residue of histone H3 was trimethylated in wild-type cells at the late stages, while only small amounts of the dimethylated form were detected. Trimethylation and dimethylation of this residue were not detected in strains deleted for SWD1, SWD3, SET1, BRE2, or SDC1. Trimethylated lysine 4 was apparent only at the early stages (48 and 96 h) of fermentation in an spp1 strain. This work indicates that the COMPASS complex represses the expression of maltose utilization genes during the late stages of fermentation of a high concentration of maltose.
在酿酒酵母中，编码麦芽糖通透酶和麦芽糖酶的基因位于不同染色体的端粒区域。COMPASS甲基化复合物可使组蛋白H3上的赖氨酸4发生甲基化，从而控制端粒区域的沉默。缺失编码COMPASS复合物组分的SWD1、SWD3、SDC1、SET1、BRE2或SPP1的酵母菌株，在含有22%麦芽糖的培养基中发酵时，其衰减程度明显高于野生型，乙醇产量最多可提高29%。效果最差的菌株是spp1。缺失COMPASS组分对含20%葡萄糖、20%蔗糖或16%麦芽糖的培养基发酵没有影响。缺失SWD3导致在22%麦芽糖发酵后期，编码麦芽糖酶的MAL12转录本数量增加。对麦芽糖酶活性和麦芽糖摄取能力也有类似影响。在野生型细胞中，组蛋白H3的赖氨酸4残基在后期发生三甲基化，而仅检测到少量二甲基化形式。在缺失SWD1、SWD3、SET1、BRE2或SDC1的菌株中未检测到该残基的三甲基化和二甲基化。在spp1菌株中，三甲基化的赖氨酸4仅在发酵早期（48小时和96小时）出现。这项研究表明，COMPASS复合物在高浓度麦芽糖发酵后期抑制麦芽糖利用基因的表达。
