Ned J.C. Lamb

Bio: Ned J.C. Lamb is an academic researcher from Centre national de la recherche scientifique. The author has contributed to research in topics: Cell cycle & Protein kinase A. The author has an hindex of 50, co-authored 90 publications receiving 10555 citations. Previous affiliations of Ned J.C. Lamb include Cold Spring Harbor Laboratory & Oregon Health & Science University.

Phosphorylated CREB binds specifically to the nuclear protein CBP

Abstract: Cyclic AMP-regulated gene expression frequently involves a DNA element known as the cAMP-regulated enhancer (CRE). Many transcription factors bind to this element, including the protein CREB, which is activated as a result of phosphorylation by protein kinase A. This modification stimulates interaction with one or more of the general transcription factors or, alternatively, allows recruitment of a co-activator. Here we report that CREB phosphorylated by protein kinase A binds specifically to a nuclear protein of M(r) 265K which we term CBP (for CREB-binding protein). Fusion of a heterologous DNA-binding domain to the amino terminus of CBP enables the chimaeric protein to function as a protein kinase A-regulated transcriptional activator. We propose that CBP may participate in cAMP-regulated gene expression by interacting with the activated phosphorylated form of CREB.

p70s6k function is essential for G1 progression.

Abstract: An essential step in the pathway by which growth factors trigger cellular proliferation is the induction of high levels of protein synthesis. This appears in part to be controlled by multiple phosphorylation of the ribosomal protein S6 (refs 4, 5). The main kinase responsible, p70s6k (refs 6-8), is activated through the phosphorylation of four sites clustered in a putative autoinhibitory domain, which is mediated by a signalling pathway distinct from those used by other well characterized mitogen-activated serine/threonine kinases (such as p42/p44mapk or p90rsk; refs 10, 11). Here we investigate the role of p70s6k in the mitogenic response. Microinjection of quiescent rat embryo fibroblasts with any of three distinct polyclonal antibodies to p70s6k abolishes serum-induced entry into S phase of the cell cycle. This effect is preceded by almost complete abrogation of the activation of protein synthesis and the expression of an essential immediate early gene product, c-fos. The inhibitory effect on DNA synthesis is also elicited by microinjection of the antibodies late in G1 phase, consistent with the finding that p70s6k activity remains high throughout G1.

The Muscle Regulatory Factors MyoD and Myf-5 Undergo Distinct Cell Cycle-specific Expression in Muscle Cells

Abstract: The muscle regulators MyoD and Myf-5 control cell cycle withdrawal and induction of differentiation in skeletal muscle cells. By immunofluorescence analysis, we show that MyoD and Myf-5 expression patterns become mutually exclusive when C2 cells are induced to differentiate with Myf-5 staining present in cells which fail to differentiate. Isolation of these undifferentiated cells reveals that upon serum stimulation they reenter the cell cycle, express MyoD and downregulate Myf-5. Similar regulations of MyoD and Myf-5 were observed using cultured primary myoblasts derived from satellite cells. To further analyze these regulations of MyoD and Myf-5 expression, we synchronized proliferating myoblasts. Analysis of MyoD and Myf-5 expression during cell cycle progression revealed distinct and contrasting profiles of expression. MyoD is absent in G0, peaks in mid-G1, falls to its minimum level at G1/S and reaugments from S to M. In contrast, Myf-5 protein is high in G0, decreases during G1 and reappears at the end of G1 to remain stable until mitosis. These data demonstrate that the two myogenic factors MyoD and Myf-5 undergo specific and distinct cell cycle–dependent regulation, thus establishing a correlation between the cell cycle–specific ratios of MyoD and Myf-5 and the capacity of cells to differentiate: (a) in G1, when cells express high levels of MyoD and enter differentiation; (b) in G0, when cells express high levels of Myf-5 and fail to differentiate.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

CDK inhibitors: positive and negative regulators of G1-phase progression

Abstract: Mitogen-dependent progression through the first gap phase (G1) and initiation of DNA synthesis (S phase) during the mammalian cell division cycle are cooperatively regulated by several classes of cyclin-dependent kinases (CDKs) whose activities are in turn constrained by CDK inhibitors (CKIs). CKIs that govern these events have been assigned to one of two families based on their structures and CDK targets. The first class includes the INK4 proteins (inhibitors of CDK4), so named for their ability to specifically inhibit the catalytic subunits of CDK4 and CDK6. Four such proteins [p16 (Serrano et al. 1993), p15 (Hannon and Beach 1994), p18 (Guan et al. 1994; Hirai et al. 1995), and p19 (Chan et al. 1995; Hirai et al. 1995)] are composed of multiple ankyrin repeats and bind only to CDK4 and CDK6 but not to other CDKs or to D-type cyclins. The INK4 proteins can be contrasted with more broadly acting inhibitors of the Cip/Kip family whose actions affect the activities of cyclin D-, E-, and A-dependent kinases. The latter class includes p21 (Gu et al. 1993; Harper et al. 1993; El-Deiry et al. 1993; Xiong et al. 1993a; Dulic et al. 1994; Noda et al. 1994), p27 (Polyak et al. 1994a,b; Toyoshima and Hunter 1994), and p57 (Lee et al. 1995; Matsuoka et al. 1995), all of which contain characteristic motifs within their amino-terminal moieties that enable them to bind both to cyclin and CDK subunits (Chen et al. 1995, 1996; Nakanishi et al. 1995; Warbrick et al. 1995; Lin et al. 1996; Russo et al. 1996). Based largely on in vitro experiments and in vivo overexpression studies, CKIs of the Cip/Kip family were initially thought to interfere with the activities of cyclin D-, E-, and A-dependent kinases. More recent work has altered this view and revealed that although the Cip/Kip proteins are potent inhibitors of cyclin Eand A-dependent CDK2, they act as positive regulators of cyclin Ddependent kinases. This challenges previous assumptions about how the G1/S transition of the mammalian cell cycle is governed, helps explain some enigmatic features of cell cycle control that also involve the functions of the retinoblastoma protein (Rb) and the INK4 proteins, and changes our thinking about how either p16 loss or overexpression of cyclin D-dependent kinases contribute to cancer. Here we focus on the biochemical interactions that occur between CKIs and cyclin Dand E-dependent kinases in cultured mammalian cells, emphasizing the manner by which different positive and negative regulators of the cell division cycle cooperate to govern the G1-to-S transition. To gain a more comprehensive understanding of the biology of CDK inhibitors, readers are encouraged to refer to a rapidly emerging but already extensive literature (for review, see Elledge and Harper 1994; Sherr and Roberts 1995; Chellappan et al. 1998; Hengst and Reed 1998a; Kiyokawa and Koff 1998; Nakayama 1998; Ruas and Peters 1998).

The phosphatidylinositol 3-Kinase AKT pathway in human cancer.

Abstract: One signal that is overactivated in a wide range of tumour types is the production of a phospholipid, phosphatidylinositol (3,4,5) trisphosphate, by phosphatidylinositol 3-kinase (PI3K) This lipid and the protein kinase that is activated by it — AKT — trigger a cascade of responses, from cell growth and proliferation to survival and motility, that drive tumour progression Small-molecule therapeutics that block PI3K signalling might deal a severe blow to cancer cells by blocking many aspects of the tumour-cell phenotype

Cancer Cell Cycles

Abstract: Uncontrolled cell proliferation is the hallmark of cancer, and tumor cells have typically acquired damage to genes that directly regulate their cell cycles. Genetic alterations affecting p16(INK4a) and cyclin D1, proteins that govern phosphorylation of the retinoblastoma protein (RB) and control exit from the G1 phase of the cell cycle, are so frequent in human cancers that inactivation of this pathway may well be necessary for tumor development. Like the tumor suppressor protein p53, components of this "RB pathway," although not essential for the cell cycle per se, may participate in checkpoint functions that regulate homeostatic tissue renewal throughout life.