TetR家族转录调控因子配体的研究进展

TetR家族转录调控因子(TetR family transcriptional regulators,TFRs)广泛分布于细菌与古菌中,最早被发现的是可控制大肠杆菌四环素外排泵的TetR。TFRs拥有DNA结合和多样的配体感知能力,其作用机制复杂。配体小分子诱导TFRs产生构象变化,抑制或促进TFRs对其靶点的控制。目前已知的TFRs配体种类繁多,包括糖类、蛋白质、脂肪酸及其衍生物、金属离子等。配体的多样性使得TFRs调节范围很广,包括从基础碳代谢、氮代谢到群体感应、抗生素生物合成等一系列生理过程。文中主要从介导调控角度介绍TFRs配体的研究进展,并结合笔者实验室的研究工作,重点阐述TFRs配体在基础碳代谢、脂肪酸生物合成与降解等初级和次级代谢产物合成过程中的作用机制,及其在基因线路开发和抗生素合成基因的激活等应用方面的研究进展。

Inactivation of SACE_3446, a TetR family transcriptional regulator, stimulates erythromycin production in Saccharopolyspora erythraea

Erythromycin A is a widely used antibiotic produced by Saccharopolyspora erythraea;however,its biosynthetic cluster lacks a regulatory gene,limiting the yield enhancement via regulation engineering of S.erythraea.Herein,six TetR family transcriptional regulators(TFRs)belonging to three genomic context types were individually inactivated in S.erythraea A226,and one of them,SACE_3446,was proved to play a negative role in regulating erythromycin biosynthesis.EMSA and qRT-PCR analysis revealed that SACE_3446 covering intact N-terminal DNA binding domain specifically bound to the promoter regions of erythromycin biosynthetic gene eryAI,the resistant gene ermE and the adjacent gene SACE_3447(encoding a longchain fatty-acid CoA ligase),and repressed their transcription.Furthermore,we explored the interaction relationships of SACE_3446 and previously identified TFRs(SACE_3986 and SACE_7301)associated with erythromycin production.Given demonstrated relatively independent regulation mode of SACE_3446 and SACE_3986 in erythromycin biosynthesis,we individually and concomitantly inactivated them in an industrial S.erythraea WB.Compared with WB,the WBΔ3446 and WBΔ3446Δ3986 mutants respectively displayed 36%and 65%yield enhancement of erythromycin A,following significantly elevated transcription of eryAI and ermE.When cultured in a 5 L fermentor,erythromycin A ofWBΔ3446 and WBΔ3446Δ3986 successively reached 4095 mg/L and 4670 mg/L with 23%and 41%production improvement relative to WB.The strategy reported here will be useful to improve antibiotics production in other industrial actinomycete.

Intermittent Geocast Routing in Urban Vehicular Delay Tolerant Networks

Nowadays, both vehicular active safety service and user infotainment service have become two core applications for urban Vehicular Delay Tolerant Networks（u VDTNs）. Both core applications require a high data transmission capacity over u VDTNs. In addition, the connection between any two vehicles in u VDTNs is intermittent and opportunistic. Intermittent data dissemination over u VDTNs is a stringent and challenging issue. In this paper,we propose Intermittent Geocast Routing（IGR）. For the first step, IGR has to estimate the active connection time interval via the moving directions and velocities between any two vehicles. Second, the throughput function for u VDTNs is fitted by building a wavelet neural network traffic model. Third, the throughput function within the effective connection time interval is integrated to obtain the forwarding capability estimation of the node. Fourth, a high-efficiency geocast routing algorithm using the node forwarding capability for u VDTNs is designed. Finally, IGR is simulated on the opportunistic Network Environment simulator. Experimental results show that IGR can greatly improve the packet delivery ratio, transmission delay, delay jitter, and packet loss rate compared with the state of the art.