Primary structure of the human fgr proto-oncogene product p55c-fgr.

Abstract

Normal human c-fgr cDNA clones were constructed by using normal peripheral blood mononuclear cell mRNA as a template. Nucleotide sequence analysis of two such clones revealed a 1,587-base-pair-long open reading frame which predicted the primary amino acid sequence of the c-fgr translational product. Homology of this protein with the v-fgr translational product stretched from codons 128 to 516, where 32 differences among 388 codons were observed. Sequence similarity with human c-src, c-yes, and fyn translational products began at amino acid position 76 of the predicted c-fgr protein and extended nearly to its C-terminus. In contrast, the stretch of 75 amino acids at the N-terminus demonstrated a greatly reduced degree of relatedness to these same proteins. To verify the deduced amino acid sequence, antibodies were prepared against peptides representing amino-and carboxy-terminal regions of the predicted c-fgr translational product. Both antibodies specifically recognized a 55-kilodalton protein expressed in COS-1 cells transfected with a c-fgr cDNA expression plasmid. Moreover, the same protein was immunoprecipitated from an Epstein-Barr virus-infected Burkitt's lymphoma cell line which expressed c-fgr mRNA but not in its uninfected fgr mRNA-negative counterpart. These findings identified the 55-kilodalton protein as the product of the human fgr protooncogene.

Structure and expression of c-fgr protooncogene mRNA in Epstein-Barr virus converted cell lines

“…On the basis of the numbers of cDNA clones of each type isolated, the downstream polyadenylation site appears to be used most frequently, Alternative polyadenylation does not account for the size difference between the 2.9kb and 3.5kb c-fgr transcripts but probably contributes to heterogeneity in the lower molecular weight band on Northern blots. This result agrees with recent data from Katamine et al (1988), which suggests that the 3.5 kb transcript is an incompletely processed precursor, containing intron 2 of the c-fgr gene. Several genes have been characterised which contain alternative polyadenylation sites.…”

“…In addition, the fyn protein has homology to the sequfence Ile-Pro-Asn-Tyr-SerAsn-Phe found at positions [50][51][52][53][54][55][56][57] (Figures 2 and 3), is identical to that reported by Inoue et al (1987), starting 3 bp downstream of their sequence. However, both our sequence and that of Inoue et al (1987) differ in the 5' untranslated region from that reported by Katamine et al (1988). This latter sequence was derived from a cDNA clone representing an incompletely processed c-fgr transcript containing intron 2.…”

“…It is therefore likely that the sequence of the 5' untranslated region reported by Katamine et al (1988) is in fact derived from intron 1, and that the sequence shown in Figure 3 is that of the 5' untranslated region of the mature mRNA.…”

“…As shown here, the 5' untranslated region of the c-fgr mRNA contains two AUG codons, both of which are outof-frame with respect to the initiating AUG. One of these, at nucleotides 101-103, obeys the rules of Kozak (1987) and so could be recognised by the 40S mammalian ribosomal subunit and be used to initiate translation, masking the authentic AUG. Kozak (1987) (Proudfoot & Brownlee, 1976), but UAUAAA, a sequence which has also been found to be used as a polyadenylation signal in the gene encoding hepatitis B virus surface antigen (McLauchlan et al, 1985). The c-fgr cDNA clones of Inoue et al (1987) and Katamine et al (1988) have the extended 3' end of pFal, and the data of Katamine et al (1988) show that the RNA species from which their cDNA clones derive are polyadenylated 13bp downstream of the 3' end of pFal, presumably using the non-consensus polyadenylation signal AGUAAA encoded at nucleotides 2335-2340. This sequence is also used as a polyadenylation signal in the genomes of baboon erythroblastosis virus and mouse mammary tumour virus (McLauchlan et al, 1985).…”

Primary structure of the brain alpha-spectrin [published erratum appears in J Cell Biol 1989 Mar;108(3):following 1175]

“…The two numbers on the right are taken from these pairwise comparisons and, again, refer to the number of identical (asterisks) and total conserved (asterisks and vertical lines) residues. The sequences are taken from the following references: c-src, Takeya and Hanafusa, 1982;fyn, Kawakami et al, 1986 andSemba et al, 1986;v-src, Takeya andHanafusa, 1982 andTaylor andHanafusa, 1983; fgr, Katamine et al, 1988;lyn, Yamanashi et al, 1987;c-yes, Sukegawa et al, 1987;hck, Quintreli et al, 1987;Isk, Marth et al, 1985;tkl, Strebhardt et al, 1985;v-crk, Mayer et al, 1988;PLC, Stahl et al, 1988. …”