Differentiation of Trypanosoma brucei may be stage non-specific and does not require progression of cell cycle
Differentiation of Trypanosoma brucei may be stage non-specific and does not require progression of cell cycle
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DOI：
10.1046/j.1365-2958.2003.03575.x
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发表时间：
2003-07-01
影响因子：
3.6
通讯作者：
Wang, CC
中科院分区：
文献类型：
--
作者：
Li, Y;Li, ZY;Wang, CC
细胞周期调控蛋白的泛素化和蛋白酶体降解在真核细胞周期调控中起着关键作用。利用RNA干扰（RNAi）技术对血流形式的布氏锥虫（Trypanosomabrucei），我们能够敲低26 S蛋白酶体的19 S调节复合物中的11个非ATP酶调节亚基蛋白（Rpns）中的每一个的表达。在每种情况下，敲低导致细胞停滞在G1和G2期，表明在G1/S和G2/M边界的细胞周期进程的阻断。这一发现不同于先前在T的原环形式中观察到的结果。brucei，其中单个Rpns的损失仅阻断穿过G2/M边界的通道。因此，额外的调节蛋白的蛋白酶体降解可能是以血流形式从G1期退出所必需的。监测11种Rpn耗尽的血流形式细胞系中的每一种向原环形式的体外分化。各细胞系与野生型细胞一样继续完成分化过程，分化细胞的总百分比约等于G1和G2细胞的总和。因此，被困在G1或G2期的细胞显然仍然可以进入并完成分化过程，这可能既不是阶段特异性的，也不依赖于T细胞的进展。布鲁氏菌细胞周期这一过程可能是在柠檬酸盐和顺乌头酸盐存在下，温度从37 ℃降至26 ℃诱导锥虫基因表达的简单模式变化。
Ubiquitination and proteasomal degradation of cell cycle regulatory proteins are known to play a pivotal role in controlling the progression of the eukaryotic cell cycle. Using the technique of RNA interference (RNAi) on the bloodstream form of Trypanosoma brucei , we were able to knock down expression of each of the 11 non-ATPase regulatory subunit proteins (Rpns) in the 19S regulatory complex of the 26S proteasome. In each case, the knock-down led to arrest of cells within the G1 and G2 phases, suggesting blockage of cell cycle progression at both G1/S and G2/M boundaries. This finding differs from that observed previously in the procyclic form of T. brucei , in which loss of individual Rpns blocks only passage across the G2/M boundary. Thus, proteasomal degradation of additional regulatory protein(s) may be required for exiting from G1 phase in the bloodstream form. In vitro differentiation of each of the 11 Rpn-depleted bloodstream form cell lines into the procyclic form was monitored. Each cell line proceeded to completion of the differentiation process like the wild-type cells with the total percentage of differentiated cells about equivalent to the sum of G1 and G2 cells. Thus, cells trapped in either G1 or G2 phase can apparently still enter and complete the process of differentiation, which is probably neither stage specific nor dependent on the progression of the T. brucei cell cycle. The process is probably a simple pattern change of gene expression in the trypanosome induced by a temperature decrease from 37degreesC to 26degreesC in the presence of citrate and cis- aconitate.