Primary structure and compartmentalization of Drosophila melanogaster host cell factor.
Human host cell factor-1 (HCF-1) is a large, 2035-residue nuclear protein that interacts with cellular and viral transcription factors. It contains an N-terminal kelch domain, C-terminal fibronectin type III (FnIII) domain, and a central region including tandem repeats which act as cleavage sites. A second human HCF-1 related gene encodes a protein with a high degree of homology in both the N-terminal kelch domain and C-terminal FnIII domain, but lacks the central portion and as a result is considerably smaller at 792 residues. A unique HCF orthologue has been found in Caenorhabditis elegans which is structurally more related to HCF-2 than HCF-1. Here we report the cloning and expression of the single Drosophila melanogaster host cell factor orthologue (dHCF). The dHCF is 1500 residues in size, intermediate between HCF-1 and HCF-2 and contains an N-terminal kelch domain, and C-terminal FnIII domain both of which show a very high degree of identity, and a central region of some 700 residues with more limited homology. Despite containing a central region no repeat-related motifs were apparent. The dHCF is expressed as a single unprocessed polypeptide consistent with the lack of the internal HCF-1 processing sites, and exhibits a predominantly nuclear localization. We show that this nuclear localization is dependent on a bipartite nuclear localization signal at the C-terminus of the protein, which contains a long spacer of 20 amino acids between two basic clusters. Finally, we also show that dHCF is unable to rescue the tsBN67 cell cycle arrest phenotype. These results indicate that dHCF is an orthologue of HCF-1, although both proteins might not be functionally exchangeable.
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Ander
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Herpesvirus Group, Marie Curie Research Institute, The Chart, Oxted, Surrey RH8 0TL, UK.
Malcomber
Sophie
S
O'Hare
Peter
P
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D006224:Cricetinae; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D005816:Genetic Complementation Test; D051863:Host Cell Factor C1; D008969:Molecular Sequence Data; D009154:Mutation; D019913:Nuclear Localization Signals / Q000235:genetics; D010641:Phenotype; D011506:Proteins / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors
D018076:DNA, Complementary; D029721:Drosophila Proteins; D051863:Host Cell Factor C1; D019913:Nuclear Localization Signals; D011506:Proteins; D014157:Transcription Factors; C473147:host cell factor, Drosophila