Localization oftheGeneforCoagulation FactorXIII a-Chain toChromosome6andIdentification ofSites ofSynthesis

Factor XIm,theclotting factor essential forcovalent stabilization ofthefibrin clot, isaheterodimer consisting ofa2andb2subunits, with catalytic function residing inthea-chain. Inorder toaddress questions regarding sites ofsynthesis andchromosomal localization oftheFactor XIIIa-chain, cDNAwascloned froma Xgtllhumanplacental cDNAlibrary. Nucleotide andamino acid sequences weredetermined fromthecDNA.Aminoacid sequencing ofpurified platelet Factor XIIIa-chains confirmed theauthenticity oftheXgtll clone. ThegeneforFactor XIIIachain wasmappeduniquely tochromosome 6.Northern blot analysis ofhumanplacental andU937(monocytelike) cell poly (A)' mRNA showed asingle - 4.0-kb message fortheFactor XIIIa-chain. These results provide conclusive evidence that the a-chain issynthesized byplacenta andmonocyte cell lines.