Membrane mu poly(A) signal and 3' flanking sequences function as a transcription terminator for immunoglobulin-encoding genes

Nucleotide sequences of all the gamma gene loci of murine immunoglobulin heavy chains

The nucleotide sequence of the entire region that encodes the gamma chains of mouse immunoglobulin was determined, namely, 11,942 bp that include the whole gamma 3 gene and 59,647 bp from the gamma 1 to the gamma 2a gene. The sequence of 21,012 bp that includes the entire human gamma 3 gene was also determined. The present analysis revealed three new findings. (1) The S regions are composed of repetitive sequences. A 26-bp repeating unit, in addition to a 49-bp repeating unit, is present in the S gamma 2b and S gamma 2a regions. In the case of the gamma 2b gene, the 26-bp unit is repeated 5 times and the 49-bp unit is repeated 69 times. In the case of the gamma 2a gene, by contrast, the 26-bp unit is repeated 63 times and the 49-bp unit is repeated 14 times. (2) Two pseudo-gamma-genes were identified between the gamma 1 and the gamma 2b genes as well as between the gamma 2b genes and the gamma 2a genes. (3) A possible functional region was identified in the region downstream of each gamma gene. This region, designated the 3' conserved region (3'CR), was also found in the region downstream of the human gamma 3 gene. Duplication of a primordial gamma 2 gene seems likely to have occurred by homologous recombination that involved the 3'CR sequences.

Carboxyl terminus structural requirements for glycosyl-phosphatidylinositol anchor addition to cell surface proteins

Glycosyl phosphatidylinositol (GPI)-anchored proteins contain in their COOH-terminal region a peptide segment that is thought to direct glycolipid addition. This signal has been shown to require a pair of small amino acids positioned 10–12 residues upstream of an hydrophobic C-terminal domain. We analysed the contribution of the region separating the anchor acceptor site and the C-terminal hydrophobic segment by introducing amino acid deletions and substitutions in the spacer element of the GPI-anchored Thy-1 glycoprotein. Deletions of 7 amino acids in this region, as well as the introduction of 2 charged residues, prevented the glycolipid addition to Thy-1, suggesting that the length and the primary sequence of the spacer domain are important determinants in the signal directing GPI anchor transfer onto a newly synthesized polypeptide. Furthermore, we tested these rules by creating a truncated form of the normally transmembranous Herpes simplex virus I glycoprotein D (gDI) and demonstrating that when its C-terminal region displays all the features of a GPI-anchored protein, it is able to direct glycolipid addition onto another cell surface molecule.