Cloning and expression of two human p70 S6 kinase polypeptides differing only at their amino termini

Journal Article · Fri Nov 01 00:00:00 EST 1991 · Molecular and Cellular Biology; (United States)

DOI:https://doi.org/10.1128/MCB.11.11.5541· OSTI ID:5144724

Grove, J R; Banerjee, P; Balasubramanyam, A; Price, D J; Avruch, J ^[1]; Coffer, P J; Woodgett, J R ^[2]

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1. Harvard Medical School, Boston, MA (United States)
2. Ludwig Inst. for Cancer Research, London (United Kingdom)

Two classes of human cDNA encoding the insulin/mitogen-activated p70 S6 kinase have been isolated; the two classes differ only in the 5{prime} region, such that the longer polypeptide consists of 525 amino acids, of which the last 502 longer residues are identical in sequence to the entire polypeptide encoded by the second cDNA. Both p70 S6 kinase polypeptides predicted by these cDNAs are present in p70 S6 kinase purified from rat liver, and each is thus expressed in vivo. Moreover, both polypeptides are expressed from a single mRNA transcribed from the (longer) p70 S6 kinase {alpha}I cDNA through the utilization of different translational start sites. Transient expression of p70 {alpha}I and {alpha}II S6 kinase cDNA in COA cells results in a 2.5- to 4-fold increase in overall S6 kinase activity. Transfection with the {alpha}II cDNA yields only the smaller set of bands, while transfection with the {alpha}I cDNA generates both sets of bands. Mutation of Met-24 in the {alpha}I cDNA to Leu or Thr suppresses synthesis of the {alpha}II polypeptides. Only the p70 {alpha}I and {alpha}II polypeptides of slowest mobility on SDS-PAGE comigrate with the 70-and 90-kDa proteins observed in purified rat liver S6 kinase. The recombinant p70 S6 kinase undergoes multiple phosphorylation and partial activation in COS cells. Acquisition of S6 protein kinase catalytic function, however, is apparently restricted to the most extensively phosphorylated recombinant polypeptides.

• OSTI ID: 5144724
• Journal Information: Molecular and Cellular Biology; (United States), Vol. 11:11; ISSN 0270-7306
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
POLYPEPTIDES
AMINO ACID SEQUENCE
RECOMBINANT DNA
DNA-CLONING
ELECTROPHORESIS
GENE RECOMBINATION
INSULIN
LEUCINE
LIVER CELLS
MITOGENS
PHOSPHOTRANSFERASES
THREONINE
AMINO ACIDS
ANIMAL CELLS
CARBOXYLIC ACIDS
CLONING
DNA
DNA HYBRIDIZATION
ENZYMES
HORMONES
HYBRIDIZATION
HYDROXY ACIDS
MOLECULAR STRUCTURE
NUCLEIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
PEPTIDE HORMONES
PEPTIDES
PHOSPHORUS-GROUP TRANSFERASES
PROTEINS
SOMATIC CELLS
TRANSFERASES
550200* - Biochemistry