- The EIF3S3 gene encoding the p40 subunit of the translation initiation factor eIF3 has eight exons and maps to the Langer-Giedion syndrome chromosome region on 8q24, but is not the TRPS1 gene. Schmidt, O., von Holtum, D., Gross, S., Horsthemke, B., Lüdecke, H.J. Hum. Genet. (1999)