Objective: To analyze the genomic structure of SNC6, a progesterone\|receptor associated protein gene and its regulatory elements in its 5'\|flanking region. Methods: Genomic sequence from GenBank database (access...Objective: To analyze the genomic structure of SNC6, a progesterone\|receptor associated protein gene and its regulatory elements in its 5'\|flanking region. Methods: Genomic sequence from GenBank database (accession number: Z98048) covering the whole SNC6 gene was used to analyze the genomic structure of SNC6 and design primers for PCR amplification of its 5'\|flanking region. A 1894 bp fragment of the 5'\|flanking region \{(-1814\} to +75) was cloned by PCR using genomic DNA from a healthy donor peripheral blood lymphocyte as template. This fragment, as well as 3 shorter derivative fragments (1423 bp, 632 bp and 416 bp, which correspond to -1344 to +75, -552 to +75 and -337 to +75 respectively), were subcloned into pGL2 series luciferase reporter vectors. These constructs were introduced into colorectal cancer cell line SW620 for transient expression of reporter gene and luciferase activities were measured. Results: The genomic structure analysis showed there are 12 exons for SNC6 gene, which spans 32017 bp (nt71529 to nt39513 in Z98048 sequence). All transfected SW620 cells with the above 5\|flanking region\|containing constructs showed luciferase activities. The highest luciferase activities were measured in transfected cells with vectors containing 1894 bp fragments, and the lowest luciferase activities were measured in transfected cells with vectors containing 416 bp fragments. Luciferase activities were higher in transfected cells with vectors containing 632 bp fragments than that in transfected cells with vectors containing 1423 bp fragments. Conclusion: The basic transcription\|promoting element (promoter) for SNC6 expression resides between 0 to -337, and two transcription\|enhancing elements (enhancer) resides between -337 to -552 and -1344 to -1814, whereas one transcription\|inhibiting element (silencer) exists between -552 to -1344.展开更多
High quality polytene chromosome maps （n=3） of a Himalayan Simuliid Simulium praelargum Datta, 1973 are presented and represent the first cytological description of a taxon found in the feuerborni group, subgenus Ne...High quality polytene chromosome maps （n=3） of a Himalayan Simuliid Simulium praelargum Datta, 1973 are presented and represent the first cytological description of a taxon found in the feuerborni group, subgenus Nevermannia. Polytene chromosomes one （I） and two （II） are metacentric, chromosome three （III） is submetacentric with the length of each chromosome occupying 37.25 %, 31.36 % and 31.34 % of the total complement length, respectively. Typical simuliid diagnostic intergeneric chromosomal markers are found within the polytene complement of this species. The nucleolar organizer （N.O.） is found at the base of the short arm of chromosome one （IS）, the Ring of Balbiani （R.B.）, double bubble （D.B.） and triad occur in the short arm of chromosome two （IIS）, the Parabalbiani Ring （EB.） and grey band （gb） occur in the long arm of chromosome two （IIL） and the Blister （BL） and Capsule （Ca） occur in the short arm of chromosome three （IIIS）.Terminal bands at the end of IIIS are heterochromatinized and present atypically with respect to other simuliid fauna. Populations studied so far are unique among the Simuliidae in that they exhibit chromosome structural monomorphism. These high resolution polytene chromosome maps will form the basis for future cytological characterization and phylogenetic comparisons amongst members of the feuerborni group展开更多
Chromosomal DNA replication is one of the central biological events occurring inside cells. Due to its large size, the replica-tion of genomic DNA in eukaryotes initiates at hundreds to tens of thousands of sites call...Chromosomal DNA replication is one of the central biological events occurring inside cells. Due to its large size, the replica-tion of genomic DNA in eukaryotes initiates at hundreds to tens of thousands of sites called DNA origins so that the replication could be completed in a limited time. Further, eukaryotic DNA replication is sophisticatedly regulated, and this regulation guarantees that each origin fires once per S phase and each segment of DNA gets duplication also once per cell cycle. The first step of replication initiation is the assembly of pre-replication complex （pre-RC）. Since 1973, four proteins, Cdc6/Cdcl8, MCM, ORC and Cdtl, have been extensively studied and proved to be pre-RC components. Recently, a novel pre-RC compo- nent called Sapl/Girdin was identified. Sapl/Girdin is required for loading Cdcl8/Cdc6 to origins for pre-RC assembly in the fission yeast and human cells, respectively. At the transition of G1 to S phase, pre-RC is activated by the two kinases, cy- clin-dependent kinase （CDK） and Dbf4-dependent kinase （DDK）, and subsequently, RPA, primase-polct, PCNA, topoisomer-ase, Cdc45, polδ and pole are recruited to DNA origins for creating two bi-directional replication forks and initiating DNA replication. As replication forks move along chromatin DNA, they frequently stall due to the presence of a great number of replication barriers on chromatin DNA, such as secondary DNA structures, protein/DNA complexes, DNA lesions, gene tran-scription. Stalled forks must require checkpoint regulation for their stabilization. Otherwise, stalled forks will collapse, which results in incomplete DNA replication and genomic instability. This short review gives a concise introduction regarding the current understanding of replication initiation and replication fork stabilization.展开更多
文摘Objective: To analyze the genomic structure of SNC6, a progesterone\|receptor associated protein gene and its regulatory elements in its 5'\|flanking region. Methods: Genomic sequence from GenBank database (accession number: Z98048) covering the whole SNC6 gene was used to analyze the genomic structure of SNC6 and design primers for PCR amplification of its 5'\|flanking region. A 1894 bp fragment of the 5'\|flanking region \{(-1814\} to +75) was cloned by PCR using genomic DNA from a healthy donor peripheral blood lymphocyte as template. This fragment, as well as 3 shorter derivative fragments (1423 bp, 632 bp and 416 bp, which correspond to -1344 to +75, -552 to +75 and -337 to +75 respectively), were subcloned into pGL2 series luciferase reporter vectors. These constructs were introduced into colorectal cancer cell line SW620 for transient expression of reporter gene and luciferase activities were measured. Results: The genomic structure analysis showed there are 12 exons for SNC6 gene, which spans 32017 bp (nt71529 to nt39513 in Z98048 sequence). All transfected SW620 cells with the above 5\|flanking region\|containing constructs showed luciferase activities. The highest luciferase activities were measured in transfected cells with vectors containing 1894 bp fragments, and the lowest luciferase activities were measured in transfected cells with vectors containing 416 bp fragments. Luciferase activities were higher in transfected cells with vectors containing 632 bp fragments than that in transfected cells with vectors containing 1423 bp fragments. Conclusion: The basic transcription\|promoting element (promoter) for SNC6 expression resides between 0 to -337, and two transcription\|enhancing elements (enhancer) resides between -337 to -552 and -1344 to -1814, whereas one transcription\|inhibiting element (silencer) exists between -552 to -1344.
文摘High quality polytene chromosome maps （n=3） of a Himalayan Simuliid Simulium praelargum Datta, 1973 are presented and represent the first cytological description of a taxon found in the feuerborni group, subgenus Nevermannia. Polytene chromosomes one （I） and two （II） are metacentric, chromosome three （III） is submetacentric with the length of each chromosome occupying 37.25 %, 31.36 % and 31.34 % of the total complement length, respectively. Typical simuliid diagnostic intergeneric chromosomal markers are found within the polytene complement of this species. The nucleolar organizer （N.O.） is found at the base of the short arm of chromosome one （IS）, the Ring of Balbiani （R.B.）, double bubble （D.B.） and triad occur in the short arm of chromosome two （IIS）, the Parabalbiani Ring （EB.） and grey band （gb） occur in the long arm of chromosome two （IIL） and the Blister （BL） and Capsule （Ca） occur in the short arm of chromosome three （IIIS）.Terminal bands at the end of IIIS are heterochromatinized and present atypically with respect to other simuliid fauna. Populations studied so far are unique among the Simuliidae in that they exhibit chromosome structural monomorphism. These high resolution polytene chromosome maps will form the basis for future cytological characterization and phylogenetic comparisons amongst members of the feuerborni group
文摘Chromosomal DNA replication is one of the central biological events occurring inside cells. Due to its large size, the replica-tion of genomic DNA in eukaryotes initiates at hundreds to tens of thousands of sites called DNA origins so that the replication could be completed in a limited time. Further, eukaryotic DNA replication is sophisticatedly regulated, and this regulation guarantees that each origin fires once per S phase and each segment of DNA gets duplication also once per cell cycle. The first step of replication initiation is the assembly of pre-replication complex （pre-RC）. Since 1973, four proteins, Cdc6/Cdcl8, MCM, ORC and Cdtl, have been extensively studied and proved to be pre-RC components. Recently, a novel pre-RC compo- nent called Sapl/Girdin was identified. Sapl/Girdin is required for loading Cdcl8/Cdc6 to origins for pre-RC assembly in the fission yeast and human cells, respectively. At the transition of G1 to S phase, pre-RC is activated by the two kinases, cy- clin-dependent kinase （CDK） and Dbf4-dependent kinase （DDK）, and subsequently, RPA, primase-polct, PCNA, topoisomer-ase, Cdc45, polδ and pole are recruited to DNA origins for creating two bi-directional replication forks and initiating DNA replication. As replication forks move along chromatin DNA, they frequently stall due to the presence of a great number of replication barriers on chromatin DNA, such as secondary DNA structures, protein/DNA complexes, DNA lesions, gene tran-scription. Stalled forks must require checkpoint regulation for their stabilization. Otherwise, stalled forks will collapse, which results in incomplete DNA replication and genomic instability. This short review gives a concise introduction regarding the current understanding of replication initiation and replication fork stabilization.
