Tyrosyl kinases acquired from anchorage-independent cells by a membrane-enveloped virus

Role of the cytoskeleton during early development

Oocytes, eggs, and embryos from a diverse array of species have evolved cytoskeletal specializations which allow them to meet the needs of early embryogenesis. While each species studied possesses one or more specializations which are unique, several cytoskeletal features are widely conserved across different animal phyla. These features include highly-developed cortical cytoskeletal domains associated with developmental information, microtubule-mediated pronuclear transport, and rapid intracellular signal-regulated control of cytoskeletal organization.

Two distinct protein kinase activities in vesicular stomatitis virions phosphorylate the NS transcription factor

Two vesicular stomatitis virion proteins, NS and M, are phosphorylated in vivo before packaging and in vitro during the transcription process carried out with disrupted virions. Phosphorylation of NS is thought to be essential for transcription but which of the many acceptor sites is or are involved in this function and which protein kinase(s) is responsible still need to be resolved. We recently reported that the virion-associated kinase which modifies M protein is most likely a different enzyme than that phosphorylating NS (Beckes et al., Virology 169, 161-171 1989). Here we present additional evidence for the presence of distinct enzymes modifying M vs NS substrates and also show that at least two distinct kinase activities modify NS protein. Each of the three activities displayed different optimum reaction conditions, phosphate donor preferences, and sensitivity to inhibition by N-ethylmaleimide.

Phosphorylation of vesicular stomatitis virus M protein: evidence for a second virion-associated protein serine kinase activity

The vesicular stomatitis virus (VSV) NS and M proteins are not only phosphorylated in vivo but are also further modified by the virion-associated protein kinase(s) concomitantly with the in vitro transcription process. Although NS phosphorylation is necessary for this transcription, no function has yet been ascribed for M protein phosphorylation. We show here that all phosphates added to M protein in vitro mapped to the trypsin-sensitive N-terminal basic domain (residues 1-43). The major site(s) (approximately 93%) corresponded to one or more of three serine residues within the first 17 amino acids. Nearly 1 mol phosphate/mol protein was added in vitro under optimal conditions suggesting that only one of these three candidate serine residues corresponds to the major site. This same M protein domain is thought to play an important role in virus RNA synthesis by inhibiting transcription. We show here that in vitro phosphorylation did not appear to affect this function. Two critical serine residues in the VSV NS protein were previously reported to be phosphorylated during in vitro transcription (D. Chattopadhyay and A. K. Banerjee, 1987, Cell 49, 407-414). The sequence flanking these NS serines is very acidic while that of all three candidate phosphoserines in the M protein is very basic. We therefore predict that at least two distinct serine-specific kinase activities are packaged in virions, one specific for M and one specific for NS.

Viral products in cells infected with vesicular stomatitis virus and superinfected with Rous sarcoma virus

In cells infected with Vesicular Stomatitis virus (VSV) ts 1026 and superinfected with Rous Sarcoma virus (RSV) synthesis of vsrc mRNA and RSV env mRNA decreases. In these cells post-translational processing of RSV precursor proteins is impaired and small amounts of VSV antigens are detected.