The shaded bars represent additional less well conserved parts of the proteins. Green bars indicate SH2 domains, blue bars indicate WD-40 repeats, pink bars indicate ankyrin repeats, apricot bars indicate SPRY domains, magenta bars indicate GTPase domains, and yellow bars represent the SOCS box. ( A) Schematic representation of the structures of SOCS, WSB, SSB, ASB, and GTPase proteins. cDNA Cloning.įigure 1 Comparison of the amino acid sequence of the SOCS proteins. A summary of the ESTs encoding SOCS-4 to SOCS-7, WSB-1 and WSB-2, SSB-1 to SSB-3, and ASB-1 to ASB-3 can be found at. Final consensus nucleotide sequences were then translated by using sequence navigator (Applied Biosystems). This process was repeated until no additional ESTs could be recovered. Again, positive ESTs were retrieved and added to the contig. Consensus nucleotide sequences derived from overlapping ESTs were then used to search the various databases with blastn ( 13).
#SOCSS FORM SOFTWARE#
By using the software package SRS ( 12), ESTs that exhibited similarity to the SOCS box (and their partners derived from sequencing the other end of cDNAs) were retrieved and assembled into contigs by using autoassembler (Applied Biosystems). The National Center for Biotechnology Information genetic sequence database (GenBank), which encompasses the major database of expressed sequence tags (ESTs) and The Institute of Genetic Research database of human ESTs were searched for sequences with similarity to a consensus SOCS box sequence by using the tfasta and motif/pattern algorithms ( 10, 11). The function of the WSB, SSB, and ASB protein families remains to be determined. The expression of representative members of each class of proteins differs markedly, as does the regulation of expression by cytokines. In addition, we show that a class of small GTPases also contains a SOCS box. In addition to four new SOCS proteins (SOCS-4 to SOCS-7) containing an SH2 domain and a SOCS box, we describe three new families of proteins that contain either WD-40 repeats (WSB-1 and -2), SPRY domains (SSB-1 to -3) or ankyrin repeats (ASB-1 to -3) N-terminal of the SOCS box. These proteins fall into five classes based on the protein motifs found N-terminal of the SOCS box. By using the SOCS box amino acid sequence consensus, we have searched DNA databases and have identified a further 16 proteins that contain this motif.
Structurally, the SOCS proteins are composed of an N-terminal region of variable length and amino acid composition, a central SH2 domain, and a previously unrecognized C-terminal motif that we have called the SOCS box. The four members of the recently identified suppressor of cytokines signaling family (SOCS-1, SOCS-2, SOCS-3, and CIS, where CIS is cytokine-inducible SH2-containing protein) appear, by various means, to negatively regulate cytokine signal transduction.
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