title: YakA, a protein kinase required for the transition from growth to development in Dictyostelium.
abstract: When Dictyostelium cells starve they arrest their growth and induce the expression of genes necessary for development. We have identified and characterized a protein kinase, YakA, that is essential for the proper regulation of both events. Amino acid sequence and functional similarities indicate that YakA is a homolog of Yak1p, a growth-regulating protein kinase in S. cerevisiae. Purified YakA expressed in E. coli is able to phosphorylate myelin basic protein. YakA-null cells are smaller and their cell cycle is accelerated relative to wild-type cells. When starved, YakA-null cells fail to decrease the expression of the growth-stage gene cprD, and do not induce the expression of genes required for the earliest stages of development. YakA mRNA levels increase during exponential growth and reach a maximum at the point of starvation, consistent with a role in mediating starvation responses. YakA mRNA also accumulates when cells are grown in medium conditioned by cells grown to high density, suggesting that yakA expression is under the control of an extracellular signal that accumulates during growth. Expression of yakA from a conditional promoter causes cell-cycle arrest in nutrient-rich medium and promotes developmental events, such as the expression of genes required for cAMP signaling. YakA appears to regulate the transition from growth to development in Dictyostelium.
authors.affiliation: Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: G M
authors.initials: GM
authors.lastname: Souza
authors.forename: S
authors.initials: S
authors.lastname: Lu
authors.forename: A
authors.initials: A
authors.lastname: Kuspa
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002453:Cell Cycle; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D004023:Dictyostelium / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D005786:Gene Expression Regulation; D017125:Genes, Protozoan; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016053:RNA, Protozoan / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D015398:Signal Transduction
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D016053:RNA, Protozoan; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D000242:Cyclic AMP; D011494:Protein Kinases; C113280:YakA protein, Dictyostelium discoideum; D017346:Protein Serine-Threonine Kinases; C062391:YAK1 protein, S cerevisiae; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases