Cold Spring Harbor Laboratory

About: Cold Spring Harbor Laboratory is a nonprofit organization based out in Cold Spring Harbor, New York, United States. It is known for research contribution in the topics: Gene & Genome. The organization has 3772 authors who have published 6603 publications receiving 1010873 citations. The organization is also known as: CSHL.

ramosa2 Encodes a LATERAL ORGAN BOUNDARY Domain Protein That Determines the Fate of Stem Cells in Branch Meristems of Maize

Abstract: Genetic control of grass inflorescence architecture is critical given that cereal seeds provide most of the world's food. Seeds are borne on axillary branches, which arise from groups of stem cells in axils of leaves and whose branching patterns dictate most of the variation in plant form. Normal maize (Zea mays) ears are unbranched, and tassels have long branches only at their base. The ramosa2 (ra2) mutant of maize has increased branching with short branches replaced by long, indeterminate ones. ra2 was cloned by chromosome walking and shown to encode a LATERAL ORGAN BOUNDARY domain transcription factor. ra2 is transiently expressed in a group of cells that predicts the position of axillary meristem formation in inflorescences. Expression in different mutant backgrounds places ra2 upstream of other genes that regulate branch formation. The early expression of ra2 suggests that it functions in the patterning of stem cells in axillary meristems. Alignment of ra2-like sequences reveals a grass-specific domain in the C terminus that is not found in Arabidopsis thaliana. The ra2-dm allele suggests this domain is required for transcriptional activation of ra1. The ra2 expression pattern is conserved in rice (Oryza sativa), barley (Hordeum vulgare), sorghum (Sorghum bicolor), and maize, suggesting that ra2 is critical for shaping the initial steps of grass inflorescence architecture.

Cdc7p–Dbf4p kinase binds to chromatin during S phase and is regulated by both the APC and the RAD53 checkpoint pathway

Abstract: Eukaryotic cells coordinate chromosome duplication by assembly of protein complexes at origins of DNA replication and by activation of cyclin-dependent kinase and Cdc7p-Dbf4p kinase. We show in Saccharomyces cerevisiae that although Cdc7p levels are constant during the cell division cycle, Dbf4p and Cdc7p-Dbf4p kinase activity fluctuate. Dbf4p binds to chromatin near the G(1)/S-phase boundary well after binding of the minichromosome maintenance (Mcm) proteins, and it is stabilized at the non-permissive temperature in mutants of the anaphase-promoting complex, suggesting that Dbf4p is targeted for destruction by ubiquitin-mediated proteolysis. Arresting cells with hydroxyurea (HU) or with mutations in genes encoding DNA replication proteins results in a more stable, hyper-phosphorylated form of Dbf4p and an attenuated kinase activity. The Dbf4p phosphorylation in response to HU is RAD53 dependent. This suggests that an S-phase checkpoint function regulates Cdc7p-Dbf4p kinase activity. Cdc7p may also play a role in adapting from the checkpoint response since deletion of CDC7 results in HU hypersensitivity. Recombinant Cdc7p-Dbf4p kinase was purified and both subunits were autophosphorylated. Cdc7p-Dbf4p efficiently phosphorylates several proteins that are required for the initiation of DNA replication, including five of the six Mcm proteins and the p180 subunit of DNA polymerase alpha-primase.