264, 16083-16092), is identical to FTCD. Both proteins co-purify with microtubules and co-localize with membranes of the Golgi complex. The capacity of FTCD to bind both to microtubules and Golgi-derived membranes may suggest that this protein, or one of its isoforms, might have in addition to its enzymatic activity, a second physiological function in mediating interaction of Golgi-derived membranes with microtubules.

No abstract

NRK cells transformed by the McDonough strain of feline sarcoma virus (SM-FeSV) were mutagenized by the use of 5'-azacytidine. Four cell lines expressing different transformation-defective phenotypes were isolated. Superinfection of these cell lines with simian sarcoma-associated virus (SSAV) led in three instances to the recovery of transforming virus particles carrying an intact fms gene. A nonconditional transformationdefective virus, designated td26-SM-FeSV (SSAV), was isolated from one of the cell lines. NRK cells infected with this mutant contained actin cables and fibronectin networks and exhibited normal cell morphology. Such cells formed only small colonies in soft agar and exhibited a mitogenic activity similar to that of noninfected cells. Cells infected with td26-SM-FeSV (SSAV) synthesized a gag-fms fusion glycoprotein (gplj9ag-fms). This polypeptide was processed in the normal manner into the intracellular gpl2Ov-fms and a transformationdefective gp14Otd-v-fms which was expressed at the surface of infected cells. This species had an increased electrophoretic mobility on polyacrylamide gels compared with the molecule from wild-type virus. gp14Otd-v-fms had endo-oN -acetylglucosaminidase H-resistant carbohydrate side chains. No tyrosine kinase activity was detectable in vivo in td26-SM-FeSV (SSAV)-infected cells even when the cells were treated with sodium orthovanadate. In vitro, fms molecules from td26-SM-FeSV (SSAV)-infected cells exhibited tyrosine kinase activity as determined by autophosphorylation and phosphorylation of exogenous (poly)Glu-Tyr. At low ATP concentrations (<5 ,uM) this in vitro tyrosine kinase activity was significantly reduced compared with that of the wild-type counterpart.

The v-fms oncogene product of the McDonough strain of feline sarcoma virus is a member of the receptor tyrosine kinase family. Its cellular counterpart, the c-fms product, is the receptor for colony-stimulating factor 1 (CSF-1) of macrophages. We have reanalyzed the v-fms gene by direct sequencing of a biologically active clone. An additional A nucleotide was detected in position 2810 of the published v-fms sequence. The frameshift changed the COOH-terminal sequence of the v-fms protein from-R-937-G-P-P-L-COOH to-Q-937-R-T-P-P-V-A-R-COOH. Antibodies against a synthetic peptide representing this new sequence precipitated the v-fms proteins from transformed NRK cells as well as from feline sarcoma virus (McDonough)-infected feline fibroblasts. We show by tryptic peptide mapping that threonine 939 present in the new sequence is phosphorylated by a yet unknown serine/threonine kinase in vivo. In chicken fibroblasts expressing the v-fms gene, this phosphorylation clearly depended on the addition of exogenous CSF-1. Furthermore, addition of CSF-1 appeared to activate the serine/threonine kinase, as judged by phosphorylation of the synthetic peptide QRTPPVAR.

S,gnal transducuon reduced by epidermal growth factor (EGF) vm ,ts receptor revolves two second messengers, chacylglycerol (DG) and momtol msphosphate, both products of phosphandylmo~to|-specdic phosphohpase C wluch seem to pamctpate m the regulauon of cellular prohferauon by EGF We observed that A431 cells and HeL~ cells m response to EGF accumulate substanual amounts of phosphauchc actd (PA), the potenual product of DG kmase However, PA appears earher and stays longer elevated than expected from DG avadabxhty thus rinsing the poss~bd~ty of an EGF-mduced acuvatxon of a phosphohpase D (PLD) In the presence of prm=ry alcohols PLD effects the phosphandyl transfer reacuon producmg PA-alcohol, a reacuon known to be excluszvely ~ by PLD m mtact cells A431 cells and cells prelabeled w~th [14C]-oleate produce m the presence of ethanol (0 5%) or l-butanol (0 2%) substanual amounts of labeled PA-alcohol m response to EGF These results mchcate that acuvauon of PLD had occurred Acuvauon of PLD may x~present a novel mgnal transducing pathway wluch may pamctpate m the regulauon of cell prohferauon by EGF -a hypothes~s presently mvesugated m thts laboratory Supported by the Deutsche Forschungsgememschaft.