Multiple Proline-rich Regions of GAP-associated Phosphoprotein p62 Bind with Different Affinities to the Src Homology 3 Domains of Fyn and Src

Several proteins of Jurkat cells were identified on SDS-PAGE gels by Coomassie Blue staining that bound specifically to affinity matrices made of five different Src homology 3 (SH3) domains fused to glutathione S-transferase (GST). Purification of the major specific band of approximately 70kDa with affinity beads of the SH3 domain of Fyn tyrosine kinase resulted in an identification of a GAP-associated p62-related protein as a ligand to the Fyn and Src SH3 domains. Indeed, from a lysate of a Rous sarcoma virus-transformed rat fibroblast line, Src co-precipitated with the 70kDa and also bound to a puta-tive SH3 binding sequence of p62. Bacterially expressed GST fusion proteins containing sequences encompassing each of the proline-rich putative SH3 binding sites of p62 bound to a subset of SH3 domains with different affinities. Phos-pholipase Cgannma 2-SH3 also revealed strong binding to the bacterially expressed p62 fusion proteins in vitro but did not show primary binding to the cellular 70kDa. The multiple SH3 binding sequences with different affinities to various SH3 mole-cules together with their phosphorylation on tyrosine residue(s) suggest a role of p62 as a foothold on which signal transduction proteins, including Src-family kinases, link together

Cloning of a cDNA for the Human Cell Adhesion Kinase β

Cell adhesion kinase beta (CAKbeta) is the second protein-tyrosine kinase (PTK) of the focal adhesion kinase (FAK) subfamily with large N- and C-domains in addition to the central kinase domain but without Src homology 2 and 3 (SH-2 and SH-3) domains. In this paper, cloning and sequencing of a cDNA encoding human CAKβ are described. A full-length clone (clone B) contained 4,157- base pairs of human CAKβ cDNA including 243-base pairs of the 5\u27-untranslated sequence and 881-base pairs of the 3\u27-untranslated sequence with a polyadenyla-tion signal (ATTAAA). The clone B of human CAKβ cDNA has an open read-ing frame encoding 1009 amino acid residues ; the human CAKβ has the same number of amino acid residues in the N-, C-, and kinase-domains as rat CAKβ . The amino acid sequence of human CAKβ is 95.4% identical with that of rat CAKβ . The species difference is most prominent in the C-domain. All three previously-recognized, subfamily-specific residues in the kinase domains of FAK and the rat CAKβ are also found in the human CAKβ . The residues V??? and A???, which have been considered to be characteristic to CAKβ , are found to be conserved also in the human CAK? . It has been postulated that CAKβ is important as a docking protein. The autophosphorylation site and also the ligand site to the SH-2 domains of the Src-family PTKs, Y???AEI, are found to be conserved in the human CAKβ . The ligand sequence for the Grb2 SH-2 domain, Y???HNV of the rat CAKβ , is found functionally conserved in the human CAKβ , Y???LNV. The third ligand sequence, E???PPPKPSR, participating in the binding to the SH-3 domains of pp130cas and Efs, is also found conserved in the human CAKβ . The extreme N- terminal 88 amino acid residues of the rat CAKβ were previously found entirely different from FAK and found unique to CAK? . Ninety four percent of those 88 residues in the human CAKβ are found identical with the rat CAKβ . This high sequence homology strongly suggeststhat this region is involved in the specific function of CAKβ different from FAK

Whole-genome characterization of human group C rotaviruses: identification of two lineages in the VP3 gene

Group C rotavirus (GCRV) is distributed worldwide as an enteric pathogen in humans and animals. However, to date, whole-genome sequences are available only for a human strain (Bristol) and a porcine strain (Cowden). To investigate the genetic diversity of human GCRVs, nearly full-length sequences of all 11 RNA segments were determined for human GCRVs detected recently in India (v508), Bangladesh (BS347), China (Wu82 and YNR001) and Japan (OH567 and BK0830) and analysed phylogenetically with sequence data for GCRVs published previously. All the RNA segments of human GCRV strains except for the VP3 gene showed high levels of conservation (>93 % nucleotide sequence identity, >92 % amino acid sequence identity), belonging to a single genetic cluster distinct from those of animal GCRVs. In contrast, the VP3 genes of human GCRVs could be discriminated into two clusters, designated M2 and M3, that were distinguished phylogenetically from those of porcine and bovine GCRVs (clusters M1 and M4, respectively). Between M2 and M3, amino acid sequence identity of the VP3 gene was 84.1–84.7 %, whereas high identities were observed within each cluster (92.3–97.6 % for M2, 98.2–99.3 % for M3). Sequence divergence among the four VP3 clusters was observed throughout the amino acid sequence except for conserved motifs, including those possibly related to enzyme functions of VP3. The presence of obvious genetic diversity only in the VP3 gene among human GCRVs suggested that either the M2 or M3 VP3 gene of human GCRVs might have been derived through reassortment from an animal GCRV or from an unidentified human GCRV strain belonging to a novel genogroup

Adenovirus E4orf6 targets pp32/LANP to control the fate of ARE-containing mRNAs by perturbing the CRM1-dependent mechanism

E4orf6 plays an important role in the transportation of cellular and viral mRNAs and is known as an oncogene product of adenovirus. Here, we show that E4orf6 interacts with pp32/leucine-rich acidic nuclear protein (LANP). E4orf6 exports pp32/LANP from the nucleus to the cytoplasm with its binding partner, HuR, which binds to an AU-rich element (ARE) present within many protooncogene and cytokine mRNAs. We found that ARE-mRNAs, such as c-fos, c-myc, and cyclooxygenase-2, were also exported to and stabilized in the cytoplasm of E4orf6-expressing cells. The oncodomain of E4orf6 was necessary for both binding to pp32/LANP and effect for ARE-mRNA. C-fos mRNA was exported together with E4orf6, E1B-55kD, pp32/LANP, and HuR proteins. Moreover, inhibition of the CRM1-dependent export pathway failed to block the export of ARE-mRNAs mediated by E4orf6. Thus, E4orf6 interacts with pp32/LANP to modulate the fate of ARE-mRNAs by altering the CRM1-dependent export pathway

CrkL directs ASAP1 to peripheral focal adhesions

Searching for proteins in platelets that can interact with the N-terminal SH3 domain of CrkL (using a combination of a pull-down assay followed by mass spectrometry), we have found that human platelets express an ADP-ribosylation factor (Arf)-specific GTPase-activating protein (GAP), ASAP1, as a CrkL-binding protein. In spreading platelets, most endogenous ASAP1 is localized at peripheral focal adhesions. To determine the physiologic significance of the CrkL-ASAP1 association, we overexpressed CrkL, ASAP1, or both in combination in COS7 cells. Unlike endogenous ASAP1 in platelets, overexpressed ASAP1 showed diffuse cytoplasmic distribution. However, when co-expressed with wild-type CrkL, both endogenous and expressed ASAP1 accumulated at CrkL-induced focal adhesions. An SH2-mutated CrkL, which cannot localize at focal adhesions, failed to recruit ASAP1 into focal adhesions. Thus, CrkL appears to be a lynchpin between ASAP1 and peripheral focal adhesions

Identification of Proteins that Associate with CAKβ/PYK2

Soluble cellular proteins were pulled down together with CAK β protein tagged with FLAGepitope and expressed in 293 cells. These proteins were identified by peptide fingerprinting combined with protein identification by mass spectrometric analysis using a MALDI-TOF mass spectrometer. Seventy hits were obtained by database search. KIAA0555-related gene product, RNA binding protein 6 (DEF-3), a polybromo-1 related protein, and huntingtin interacting protein 1 (HIP-I) were among the strong candidates