University of Alabama

About: University of Alabama is a education organization based out in Tuscaloosa, Alabama, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 27323 authors who have published 48609 publications receiving 1565337 citations. The organization is also known as: Alabama & Bama.

Internet Protocol Television (IPTV): The Killer Application for the Next-Generation Internet

Abstract: Internet protocol television (IPTV) will be the killer application for the next-generation Internet and will provide exciting new revenue opportunities for service providers. However, to deploy IPTV services with a full quality of service (QoS) guarantee, many underlying technologies must be further studied. This article serves as a survey of IPTV services and the underlying technologies. Technical challenges also are identified.

Cell cycle-regulated phosphorylation of p220(NPAT) by cyclin E/Cdk2 in Cajal bodies promotes histone gene transcription.

Abstract: Cyclin E, an essential regulatory subunit of Cdk2 (Dulic et al. 1992; Koff et al. 1992), plays a central role in coordinating both the onset of S phase and centrosome duplication in multicellular eukaryotes (Sherr 1996; Reed 1997). Cyclin E/Cdk2 complexes have two major roles in promoting S phase. First, cyclin E/Cdk2 participates, together with cyclin D/Cdk4, in the control of transcriptional processes that are critical to cell cycle progression. The best understood example is control of the E2F/DP transcription factor via phosphorylation of a family of transcriptional repressors (Rb, p130, and p107) (for review, see Reed 1997; Dyson 1998; Nevins 1998). E2F complexes regulate the S-phase-dependent expression of a number of proteins required for the synthesis of nucleic acids as well as proteins such as Cdc2 and cyclin A that promote subsequent cell cycle transitions. Second, cyclin E/Cdk2 can function in an E2F-independent manner to activate DNA replication. Accumulation of cyclin E is required for S-phase entry, and ectopic cyclin E expression can bypass the requirement for Rb inactivation and E2F activation for S-phase entry (Ohtsubo et al. 1995; Leng et al. 1997; Lukas et al. 1997). An understanding of the role of cyclin E/Cdk2 in promoting S phase requires knowledge of its essential substrates. Insight into Cdk targets has been advanced by the finding that several Cdk substrates bind tightly to the cyclin subunit. In some cases, this interaction involves a motif in the substrate, the RXL motif, and a conserved pocket in the cyclin box (Zhu et al. 1995; Adams et al. 1996; Russo et al. 1996; Schulman et al. 1998; Brown et al. 1999; Ma et al. 1999). We and others have exploited this property of cyclins to identify relevant cyclin E/Cdk2 substrates with the use of expression cloning (Zhao et al. 1998; Ma et al. 1999). One of these, p220NPAT, interacts with cyclin E/Cdk2 in extracts from tissue culture cells and accelerates S-phase entry when overexpressed (Zhao et al. 1998). Moreover, retroviral insertion into the mouse p220NPAT gene leads to embryonic lethality at the eight-cell stage, indicating an essential role for p220 in cell division or development (Di Fruscio et al. 1997). However, the precise function of p220 and the role of cyclin E/Cdk2 in its action remain unknown. Emerging data (Zhao et al. 2000, this paper) suggest that p220 is involved in S-phase-specific histone gene transcription. Histones, components of nucleosomes, have to be supplied on demand during DNA replication. This regulation is attributed to both transcriptional and posttranscriptional control mechanisms (Harris et al. 1991; Heintz 1991), mediated in part by the activation of histone gene–specific transcription factors (Oct-1 in the case of the H2B promoter and H1TF2 in the case of the H1 promoter) through an unknown mechanism (Fletcher et al. 1987; Segil et al. 1991). Once generated, histone messages are stabilized and processed preferentially in S phase. Implicated in histone gene transcription are Cajal bodies (CBs; sometimes referred to as coiled bodies). CBs were initially described as small nuclear organelles (Cajal 1903), but their function has remained obscure for the better part of the twentieth century. Recent work has led to the hypothesis that CBs are sites of assembly of transcription and splicing complexes (Gall et al. 1999). The link to histone transcription comes from the finding that a subset of CBs is physically associated with histone gene clusters on chromosomes 1 (1q21) and 6 (6p21) (Frey and Matera 1995) and with histone gene loci in Xenopus lampbrush chromosomes (Abbott et al. 1999). Moreover, CBs also contain a component of the histone mRNA 3′-end processing machinery SLBP1 (Abbott et al. 1999). Here, we report that p220NPAT is localized to discrete foci that are coincident with a subset of CBs in normal diploid fibroblasts. The number of p220 foci increased from two in Go and G1 cells in association with chromosome 6 to four in S and G2 phases in association with both chromosomes 6 and 1. Foci are lost during mitosis. Consistent with these observations, Zhao et al. (2000) have found that p220 is associated directly with histone gene clusters and that overexpression of p220 can activate histone 2B and histone 4 transcription. We also demonstrate that cyclin E is contained in p220 foci and that p220 within CBs is phosphorylated on Cdk sites in a cell cycle–dependent manner. Moreover, mutation of cyclin E/Cdk2 phosphorylation sites in p220 reduces its ability to activate expression from histone H2B reporter constructs in transiently transfected cells. These data, together with those of Zhao et al. (2000), suggest that cyclin E/Cdk2 functions in conjunction with p220 to coordinate S-phase-dependent histone gene transcription; they also demonstrate a role for CBs in cell cycle–regulated transcriptional control.

Understanding physicians: Intentions to withdraw from practice: The role of job satisfaction, job stress, mental and physical health

Abstract: Health care organizations may incur high costs due to a stressed, dissatisfied physician workforce. This study proposes and tests a model relating job stress to four intentions to withdraw from practice mediated by job satisfaction and perceptions of physical and mental health.