SmMAK16, the Schistosoma mansoni homologue of MAK16 from yeast, targets protein transport to the nucleolus.
The SmMAK16 gene from Schistosoma mansoni was cloned by chance when an adult worm cDNA library was probed with antiserum to affinity-purified S. mansoni GSH S-transferases. SmMAK16 encodes a hydrophilic protein of 259 amino acids with a molecular mass of 31 kDa. The protein shares 43% sequence identity and 66% similarity to the nuclear protein MAK16 of Saccharomyces cerevisiae that has been implicated both in cell cycle progression and biogenesis of 60S ribosomal subunits. Both proteins display a similar degree of sequence similar to the hypothetical protein CeMAK16 from Caenorhabditis elegans. These proteins share a number of apparent protein motifs, including two nuclear localization signals (NLS), multiple sites for phosphorylation by protein kinase CK2 and four conserved cysteine residues that resemble a zinc binding domain. SmMAK16 mRNA is more highly expressed in adult female worm than males. Recombinant SmMAK16 was phosphorylated by human protein kinase CK2. When chimeric constructs containing SmMAK16 fused the green fluorescent protein (GFP) were transiently transfected into COS-7s cells, the reporter was localized not in nuclei, but exclusively in nucleoli. The yeast and nematode homologues were likewise able to direct nucleolar accumulation of the fluorescent reporter. The high degree of sequence conservation together with the ability to direct nucleolar protein transport supports the hypothesis that MAK16 proteins play a key role in the biogenesis of 60S subunits.
Milhon
J L
JL
Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin - Madison, Biotron Building, 2115 Observatory Drive, 53705-1087, Madison, WI, USA.
Albert
T J
TJ
Vande Waa
E A
EA
O'Leary
K A
KA
Jackson
R N
RN
Kessler
M A
MA
Schuler
L A
LA
Tracy
J W
JW
D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002466:Cell Nucleolus / Q000378:metabolism*; D003001:Cloning, Molecular; D018509:DNA, Helminth / Q000235:genetics; D005260:Female; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D049452:Green Fluorescent Proteins; D015801:Helminth Proteins / Q000378:metabolism*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D010766:Phosphorylation; D016133:Polymerase Chain Reaction / Q000379:methods; D018510:RNA, Helminth / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D012550:Schistosoma mansoni / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D018797:Cell Cycle Proteins; D018509:DNA, Helminth; D015801:Helminth Proteins; D008164:Luminescent Proteins; C097699:MAK16 protein, S cerevisiae; D018510:RNA, Helminth; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D005982:Glutathione Transferase