Molecular Cloning and Expression of a Human B-Cell Growth Factor Gene in Escherichia coli

Abstract
A human B-cell growth factor (BCGF) (12 kilodaltons) supports the clonal proliferation of B lymphocytes. A clone was isolated that contained the proper structural sequence to encode biologically active, 12-kilodalton BCGF in Escherichia coli and to hybridize to a specific messenger RNA, identified by in vitro translation in Xenopus laevis oocytes. A relatively hydrophobic region of 18 amino acids was found at the amino terminal of the 124-amino acid-long polypeptide. The carboxyl terminal is composed of at least 32 amino acids that are derived from nucleotide sequences bearing significant homology to the Alu repeat family.