We have selected yeast mutants that exhibit a constitutively active pheromone-response pathway in the absence of the beta subunit of the trimeric G protein. Genetic analysis of one such mutant ...revealed that it contained recessive mutations in two distinct genes, both of which contributed to the constitutive phenotype. One mutation identifies the RGA1 locus (Rho GTPase activating protein), which encodes a protein with homology to GAP domains and to LIM domains. Deletion of RGA1 is sufficient to activate the pathway in strains lacking the G beta subunit. Moreover, in wild-type strains, deletion of RGA1 increases signaling in the pheromone pathway, whereas over-expression of RGA1 dampens signaling, demonstrating that Rga1p functions as a negative regulator of the pheromone response pathway. The second mutation present in the original mutant proved to be an allele of a known gene, PBS2, which encodes a putative protein kinase that functions in the high osmolarity stress pathway. The pbs2 mutation enhanced the rga1 mutant phenotype, but by itself did not activate the pheromone pathway. Genetic and two-hybrid analyses indicate that an important target of Rga1p is Cdc42p, a p21 GTPase required for polarity establishment and bud emergence. This finding coupled with recent experiments with mammalian and yeast cells indicating that Cdc42p can interact with and activate Ste20p, a protein kinase that operates in the pheromone pathway, leads us to suggest that Rga1p controls the activity of Cdc42p, which in turn controls the magnitude of signaling in the pheromone pathway via Ste20p.
The mechanism that causes large regions of eukaryotic chromosomes to remain unreplicated until late in S phase is not understood. We have found that 67 kb of telomere-adjacent DNA at the right end of ...chromosome V in S. cerevisiae is replicated late in S phase. An ARS element in this region, ARS501, was shown by two-dimensional gel analysis to be an active origin of replication. Kinetic analyses indicate that the rate of replication fork movement within this late region is similar to that in early replicating regions. Therefore, the delayed replication of the region is a consequence of late origin activation. The results also support the idea that the pattern of interspersed early and late replication along the chromosomes of higher eukaryotes is a consequence of the temporal regulation of origin activation.
An understanding of how an extracellular stimulus causes changes in cell growth is emerging from the study of four signal transduction pathways in
Saccharomyces cerevisiae: the pheromone-response, ...pseudohyphal differentiation, osmolarity-response, and protein kinase C activated pathways. Each of these pathways contains at its core a distinct mitogen-activated protein kinase cascade. Biochemical and molecular studies have determined the functional order of the kinases in the pheromone-response pathway and have suggested that they are organized into a complex by a protein scaffold. The cell surface sensor system for the osmolarity-response pathway has been identified. It shows striking similarity to bacterial two-component sensor-responder systems. Finally, components that integrate information from these pathways and communicate it to cell growth regulators have been revealed.
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IJS, IMTLJ, KILJ, KISLJ, NUK, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The English learner (EL) population in the United States continues to grow. To improve their pedagogy in working with this population, many educators have received training in English as a Second ...Language (ESL), but the gap between ELs and their native English speaking peers persists. When teachers engage as members of professional support networks, they are more likely to successfully implement the strategies learned in their ESL professional development (Echevarria, Richards-Tutor, Chinn, & Ratleff, 2011). This study considered the nature and function of the professional support network of a district's ESL-endorsed teachers. Using network theory methods, 257 teachers and other school personnel responded to an online survey. Through an understanding of the professional support needs of these teachers, whom they contact for support, and the nature of those ties (in terms of reciprocity, homophily, frequency, influence, and relational embeddedness), district and school administrators can be better positioned to enhance successful professional support networks and facilitate the implementation of effective teacher practices learned through professional development. Based on the findings, practical suggestions are given to help district administrators strengthen these professional support networks with the intent to maintain compliance with governmental standards, help schools to meet federally and state-mandated progress requirements, and have a positive academic impact upon English-language learning students.
Alcohol abuse and dependence are human conditions for which no full equivalent exists in animals. Nevertheless, animal models frequently are used to study various aspects of alcohol dependence that ...cannot be easily or ethically assessed in humans, including neurobiological mechanisms underlying alcohol dependence. Many of these animal models involve rodents; however, the characteristics (i.e., phenotypes) of chronic heavy drinking may be limited in these species. Nonhuman primates add an important translational aspect to the study of alcohol abuse and alcoholism. Their genetic, anatomical, physiological, and behavioral similarity to humans offers unique opportunities for identifying risk factors that may predispose a person to or accelerate the course of alcohol addiction. Studying alcohol consumption in nonhuman primates, including the distribution of drinking levels in a population, also can be uniquely informative to alcohol research. For example, research on the self-administration procedures in primates can help scientists identify risk factors for excessive alcohol consumption in humans. The phenotype of excessive drinking then can serve as the starting point to test and verify the underlying genetic and environmental influences. The resulting findings, in turn, can help guide prevention and treatment strategies.
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DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
NF-κB essential modifier (NEMO), also known as IKK-γ, is a member of the I-κB kinase complex responsible for phosphorylating I-κB, allowing the release and activation of NF-κB. Boys with an expressed ...NEMO mutation have an X-linked syndrome characterized by hypohidrotic ectodermal dysplasia with immune deficiency (HED-ID). The immunophenotype resulting from NEMO mutation is highly variable, with deficits in both T and B cell responses. We evaluated three patients with NEMO mutations (L153R, Q403X, and C417R) and HED-ID who had evidence of defective CD40 signaling. All three patients had normal percentages of peripheral blood NK cells, but impaired NK cell cytotoxic activity. This was not due to a generalized defect in cytotoxicity because antibody-dependent cellular cytotoxicity was intact. This abnormality was partially reversed by in vitro addition of IL-2, which was also able to induce NF-κB activation. In one patient with recurrent cytomegalovirus infections, administration of IL-2 partially corrected the NK cell killing deficit. These data suggest that NEMO participates in signaling pathways leading to NK cell cytotoxicity and that IL-2 can activate NF-κB and partially overcome the NK cell defect in patients with NEMO mutations.
The temporal program of replication is one of many mysterious and intriguing features of DNA replication in eukaryotes. In an effort to understand the regulation of the temporal program in the yeast ...Saccharomyces cerevisiae, a 50 kb region of late replicating DNA on the distal right arm of chromosome V was cloned and analyzed. Using a dense to light isotope shift, combined with cell synchronization, the replication time of restriction fragments within the region were analyzed, and all were found to be duplicated within the last half of S phase. The region was also shown to contain two ARS elements, ARS 5RX, located within or adjacent to the X element of the telomere, and ARS 501, positioned 21 kb from the telomere. ARS 501 was suggested to be a late activated replication origin by the observation that it is replicated in mid-S phase, and before its flanking fragments. To determine whether origin activation time is established by origin sequence or by a chromosomal context, two complementary experiments were performed. In one, a normally early activated origin, ARS1, was integrated into the late replicating region on chromosome V. It was found that ARS1 was not activated until late in S phase when located on chromosome V. In a second experiment, normally late activated ARS 501 was cloned onto an otherwise ARS deficient plasmid; the resulting plasmid was found to be replicated early in S phase. It was concluded, therefore, that both ARS1 and ARS 501 had the ability to be active origins either early or late in S phase, and that their activation times were established by their chromosomal contexts. It was shown that by linearizing the circular ARS 501 plasmid, the origin switched from an early to late activation time. This observation suggested that either the topology of the linear plasmid or the telomere sequences on the ends of the linear plasmid, was sufficient to establish a late replication context. A circular version of the plasmid containing 450 bp of telomere sequence was not late replicating, suggesting that telomere sequences themselves are not sufficient to establish a late replication context. A 40 kb chromosomal deletion of telomere adjacent DNA was created on chromosome V-right. A DNA fragment adjacent to the chromosome V late region, shown previously to be early replicating, was examined in this strain. The repositioning of the fragment closer to the telomere resulted in that DNA becoming late replicating. These results all suggest that proximity to a chromosome end is sufficient to establish a late replication context.
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