Cyclin-specific START events and the G1-phase specificity of arrest by mating factor in budding yeast

The START cell cycle transition in the budding yeast Saccharomyces cerevisiae is catalyzed by the Cdc28 cyclin-dependent kinase associated with Cln-type cyclins. Since ectopic expression of the B-type cyclin CLB5 can efficiently rescue the inviability that results from CLN depletion, we tested the specificity of the CLN and CLB classes of cyclins for promoting START-associated events. Several aspects of the regulation of the mating factor response were compared for cells in which START activity was provided by either Cln-cyclins or Clb5. Unlike Cln1 and Cln2, high level expression of Clb5 was unable to repress the activity of the mating factor response pathway at START. Downregulation of Far1 protein at START is normal in cln−GAL1::CLB5 cells. Even though the Clb5-Cdc28 kinase activity in cln−GAL1::CLB5 cells is not downregulated in response to mating factor, cells arrest in the first cycle after addition of mating factor with a similar sensitivity as wild-type cells. However, whereas wild-type cells treated with mating factor arrest specifically in G1 phase as unbudded cells with unreplicated DNA (pre-START), most cln−GAL1::CLB5 cells arrest as budded post-START cells with replicated DNA. Our findings demonstrate the ability of post-START cells to arrest in response to mating factor and provide novel evidence for mechanisms that contribute to restrict mating factor-induced arrest in wild-type cells to the G1 phase of the cell cycle. Received: 25 September 1997 / Accepted: 9 November 1997     

Jurassic artematopodid beetles and their implications for the early evolution of Artematopodidae (Coleoptera)

Fossil Artematopodidae are rarely collected and previously confined to middle Eocene Baltic amber. Here we report the first definitive artematopodid, Sinobrevipogon jurassicus gen. et sp.n. , from the Middle Jurassic Daohugou beds (c. 165 Ma) in Inner Mongolia, northeastern China. It exhibits a number of defining features of Artematopodidae, including paired carinae on prosternum and an internal apical interlocking tongue on the ventral side of each elytron. However, it differs from any modern Artematopodidae by having the mesocoxal cavitiy closed by the mesepimeron and the anterolateral edge of metanepisternum. The discovery of this new genus represents the earliest fossil record for Artematopodidae, highlighting the antiquity of the family. The systematic positions of Forticatinius Tan & Ren and Tarsomegamerus Zhang are discussed, and the latter is formally transferred to Artematopodidae. Phylogenetic relationships within Artematopodidae were investigated to elucidate the relationships between the two Jurassic genera and Recent genera. Eleven in‐group taxa and two out‐groups were included in a cladistic analysis based on 30 adult characters; the resulting tree recovered the family Artematopodidae in three clades: (i) Electribius authority, (ii) Ctesibius authority + Brevipogon authority + Sinobrevipogon + Tarsomegamerus and (iii) the remaining Recent genera, including Allopogonia authority.     

Differences in the DNA restriction patterns between sheep with HbA and HbB

DNA samples obtained from sheep homozygous for HbA, for HbB and heterozygous were subjected to Southern blot analysis using a goat beta F and a rabbit beta 1-globin gene as probes. Sheep homozygous for HbA show a different restriction pattern from that of sheep homozygous for HbB with each of the used endonucleases. The DNAs from moufflon and sheep homozygous for HbA show indistinguishable restriction patterns with some endonucleases. By means of double digestions it has been possible to construct restriction maps of the beta B and beta C genes and to confirm the absence of the beta C gene in HbB sheep.     

拟南芥CRKs家族自抑域序列的预测

目的:以拟南芥CDPKs激酶家族为摹本,推测类结构激酶家族CRKs的自抑域.方法:以生物信息学工具phylip3.65和clustalx1.83对CDPK家族和CRK家族进行进化树构建平和多重序列比对分析.结果:结果显爪CDPK亚家族Ⅳ与CRK家族的相似程度很高,且自抑域序列区域非常保守.以此为依据预测了CRK家族各成员的自抑域序列.