Neurons are highly polarized cells with a single long axon and multiple dendrites, all of which are actinrich structures. The precise regulation of neuronal cell morphology is a fundamental aspect of neurobiology. The...Neurons are highly polarized cells with a single long axon and multiple dendrites, all of which are actinrich structures. The precise regulation of neuronal cell morphology is a fundamental aspect of neurobiology. The major role of Rho GTPases, which is conserved in all eukaryotes, is to regulate the actin and microtubule cytoskeleton. Therefore theRhoGTPases are key regulators of neuronal morphology during development besides their canonical functions in actin cytoskeletal regulation, cell migration and cell cycle progression. Semaphorins are a family of secreted or transmembrane proteins, which function through their receptor plexins and/or neuropilins to act as the repulsive or attractive guidance cues for axons and dendrites. It has been demonstrated that the fully activetion of plexins appears to be dependent on the binding of RhoGTPases to theRhobinding domain (RBD) and Semaphorin to the extracellular region. Here, we summarize the functions of the small Rho GTPases in two well-studied vertebrate Semaphorins, Sema3Aand Sema4D;and the potential roles of the small Rho GTPases in some poorly-studied vertebrate Semaphorins Sema5A, Sema6Aand Sema7A. We also summarize the functions of different members of Ras family, R-Ras, M-Ras and Rap, in Semaphorin signalling pathways as well.展开更多
Transcription attenuation in response to the availability of a specific amino acid is believed to be controlled by alternative configurations of RNA secondary structures that lead to the arrest of translation or the r...Transcription attenuation in response to the availability of a specific amino acid is believed to be controlled by alternative configurations of RNA secondary structures that lead to the arrest of translation or the release of the arrested ribosome from the leader mRNA molecule.In this study,we first report a possible example of the DnaA‐dependent riboswitch for transcription attenuation in Escherichia coli.We show that(i)DnaA regulates the transcription of the structural genes but not that of the leader hisL gene;(ii)DnaA might bind to rDnaA boxes present in the HisL‐SL RNA,and subsequently attenuate the transcription of the operon;(iii)the HisL‐SL RNA and rDnaA boxes are phylogenetically conserved and evolutionarily important;and(iv)the translating ribosome is required for deattenuation of the his operon,whereas tRNA^(His) strengthens attenuation.This mechanism seems to be phylogenetically conserved in Gram‐negative bacteria and evolutionarily important.展开更多
文摘Neurons are highly polarized cells with a single long axon and multiple dendrites, all of which are actinrich structures. The precise regulation of neuronal cell morphology is a fundamental aspect of neurobiology. The major role of Rho GTPases, which is conserved in all eukaryotes, is to regulate the actin and microtubule cytoskeleton. Therefore theRhoGTPases are key regulators of neuronal morphology during development besides their canonical functions in actin cytoskeletal regulation, cell migration and cell cycle progression. Semaphorins are a family of secreted or transmembrane proteins, which function through their receptor plexins and/or neuropilins to act as the repulsive or attractive guidance cues for axons and dendrites. It has been demonstrated that the fully activetion of plexins appears to be dependent on the binding of RhoGTPases to theRhobinding domain (RBD) and Semaphorin to the extracellular region. Here, we summarize the functions of the small Rho GTPases in two well-studied vertebrate Semaphorins, Sema3Aand Sema4D;and the potential roles of the small Rho GTPases in some poorly-studied vertebrate Semaphorins Sema5A, Sema6Aand Sema7A. We also summarize the functions of different members of Ras family, R-Ras, M-Ras and Rap, in Semaphorin signalling pathways as well.
基金supported by grants from the National Natural Science Foundation of China(Grant no.32260233 to Morigen)the Science and Technology Foundation of Inner Mongolia(Inner Mongolia Key Laboratory for Molecular Regulation of the Cell,Grant no.2021PT0002).
文摘Transcription attenuation in response to the availability of a specific amino acid is believed to be controlled by alternative configurations of RNA secondary structures that lead to the arrest of translation or the release of the arrested ribosome from the leader mRNA molecule.In this study,we first report a possible example of the DnaA‐dependent riboswitch for transcription attenuation in Escherichia coli.We show that(i)DnaA regulates the transcription of the structural genes but not that of the leader hisL gene;(ii)DnaA might bind to rDnaA boxes present in the HisL‐SL RNA,and subsequently attenuate the transcription of the operon;(iii)the HisL‐SL RNA and rDnaA boxes are phylogenetically conserved and evolutionarily important;and(iv)the translating ribosome is required for deattenuation of the his operon,whereas tRNA^(His) strengthens attenuation.This mechanism seems to be phylogenetically conserved in Gram‐negative bacteria and evolutionarily important.
