The amino acid sequences used in the alignment include full-length sequences of TTP from human (NP_003398), mouse (NP_035886), rat (P47973), bovine (P53781) and sheep (AY462109), and from partial amino terminal sequences deduced from the EST sequences of pig (AJ943797, CB288050, CB286240, DY416794 and DY419026), horse (CD536573 and CD536523), chimpanzee (CR555169 and XM_001136016), and dog (BQ172881); full-length sequences of ZFP36L1 (TIS11B) from human (Q07352), mouse (B39590) and rat (NP_058868); and full-length sequences of ZFP36L2 (TIS11D) from human (P47974) and mouse (NP_008818). The sequences were aligned with the PILEUP program of GCG software. The gaps in the horse TTP sequence represent incomplete sequence and it is probably highly similar to the other mammalian TTP sequences. The conserved sequence motifs between the subgroups are boxed and linked with a line between the corresponding boxes. The underlined amino acid residues are the four-proline residues in the three repeats of mammalian TTP. The bold amino acid residues within the sequence alignment are the CCCH residues in the tandem zinc-finger binding motifs; and the conserved serine threonine and tyrosine residues, which correspond to the phosphorylation sites in hTTP identified in our report (indicated at the top of the sequence alignment: S12, S21, S41, S43, S46, S48, S66, S88, S90, T92, S93, T95, T106, T111, Y158, S160, S169, S184, S188, T196, S197, S207, S210, S217, S218, S228, S230, S233, T238, S252, T257, T271, S273, S276, S279, and Y284, S294 and S296); and the three additional phosphorylation sites in mTTP identified previously (also indicated at the top of the sequence alignment: S60, S113 and S323 in hTTP, corresponding to S52, S105 and S316 in mTTP). The bold phosphorylation sites at the top of the alignment are the conserved phosphorylation sites in TTP, ZFP36L1 and ZFP36L2; which are linked with a line between the two conserved phosphorylation sites. A total of 40 site-directed mutants of His-hTTP were used in our study [], including 1-site mutation (10 mutants): S88A, S90A, S93A, S186A, S197A, S214A, S218A, S228A, S296A, T271A; 2-site mutation (8 mutants): S(214,218)A, S(214,2280)A, S(214,228)A, S(197, 214)A, S(197, 218)A, S(197,228)A, S(197, 296)A, S(93, 197)A; 3-site mutation (5 mutants): S(88,90,93)A, S(197,214,218)A, S(197,214,228)A, S(197,218,228)A, S(214,218,228)A; 4-site mutation (3 mutants): S(214,218,228,296)A, S(88,90,93,197)A, S(197,214,218,228)A; 5-site mutation (5 mutants): S(88,90,93,214,218)A, S(88,90,93,214,228)A, S(88,90,93,218,228)A, S(197,214,218,228,296)A, S(88,197,214,218,228)A; 6-site mutation (4 mutants): S(88,90,93,214,218,228)A, S(88,197,214,218,228,296)A, S(88,186,197,214,218,228)A, S(88,197,214,218,228)AT271A; 7-site mutation (4 mutants): S(88,186,197,214,218,228,296)A, S(88,197,214,218,228,296)T271A, S(88,90,93,214,218,228,296)A, S(88,90,93,197,214,218,228)A; 8-site mutation (1 mutant): S(88,90,93,197,214,218,228,296)A.