Multiple Skp1-related proteins in Caenorhabditis elegans: diverse patterns of interaction with Cullins and F-box proteins.
BACKGROUND
The ubiquitin-proteasome pathway of proteolysis controls the abundance of specific regulatory proteins. The SCF complex is a type of ubiquitin-protein ligase (E3) that contributes to this pathway in many biological systems. In yeast and mammals, the SCF complex consists of common components, including Skp1, Cdc53/Cul1, and Rbx1, as well as variable components known as F-box proteins. Whereas only one functional Skp1 gene is present in the human genome, the genome of Caenorhabditis elegans has now been shown to contain at least 21 Skp1-related (skr) genes. The biochemical properties, expression, and function of the C. elegans SKR proteins were examined.


RESULTS
Of the 17 SKR proteins examined, eight (SKR-1, -2, -3, -4, -7, -8, -9, and -10) were shown to interact with C. elegans CUL1 by yeast two-hybrid analysis or a coimmunoprecipitation assay in mammalian cells. Furthermore, SKR proteins exhibited diverse binding specificities for C. elegans F-box proteins. The tissue specificity of expression of the CUL1-interacting SKR proteins was also varied. Suppression of skr-1 or skr-2 genes by double-stranded RNA interference resulted in embryonic death, whereas that of skr-7, -8, -9, or -10 was associated with slow growth and morphological abnormalities.


CONCLUSIONS
The multiple C. elegans SKR proteins exhibit marked differences in their association with Cullins and F-box proteins, in tissue specificity of expression, and in phenotypes associated with functional suppression by RNAi. At least eight of the SKR proteins may, like F-box proteins, act as variable components of the SCF complex in C. elegans.
Yamanaka
Atsushi
A
Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, 812-8582, Fukuoka, Japan.
Yada
Masayoshi
M
Imaki
Hiroyuki
H
Koga
Makoto
M
Ohshima
Yasumi
Y
Nakayama
Kei-Ichi
K
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D044842:Cullin Proteins; D005786:Gene Expression Regulation; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D011485:Protein Binding; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D020798:Two-Hybrid System Techniques
D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; C100318:Cullin 1; D044842:Cullin Proteins; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; D044786:S-Phase Kinase-Associated Proteins