Phylogenetic conservation of the 3' cryptic recombination signal sequence (3'cRSS) in the VH genes of jawed vertebrates.

The VH replacement process is a RAG-mediated secondary recombination in which the variable region of a rearranged VHDJH is replaced by a different germline VH gene. In almost all human and mouse VH genes, two sequence features appear to be crucial for VH replacement. First, an embedded heptamer, which is located near the 3' end of the rearranged VH gene, serves as a cryptic recombination signal sequence (3'cRSS) for the VH replacement process. Second, a short stretch of nucleotides located downstream of the 3'cRSS serve as a footprint of the original VH region, frequently encoding charged amino acids. In this review, we show that both of these two features are conserved in the VH genes of all jawed vertebrates, which suggests that the VH replacement process may be a conserved mechanism.

Immunoglobulin genes and diversity: what we have learned from domestic animals.

This review focuses on the diversity of immunoglobulin (Ig) genes and Ig isotypes that are expressed in domestic animals. Four livestock species-cattle, sheep, pigs, and horses-express a full range of Ig heavy chains (IgHs), including µ, δ, γ, ϵ, and α. Two poultry species (chickens and ducks) express three IgH isotypes, µ, υ, and α, but not δ. The κ and λ light chains are both utilized in the four livestock species, but only the λ chain is expressed in poultry. V(D)J recombination, somatic hypermutation (SHM), and gene conversion (GC) are three distinct mechanisms by which immunoglobulin variable region diversity is generated. Different domestic animals may use distinct means to diversify rearranged variable regions of Ig genes.

Construction of a High Efficiency PCR Products Cloning T Vector Using pGEM-5zf (+).

A highly efficient cloning vector was constructed for cloning PCR products by inserting an 80 bp DNA fragment into pGEM-5zf (+) vector. The Xcm I digestion of this vector gave rise to a 3' overhanging deoxythymidine offering the possibility of cloning PCR products with 3' adenosine overhang created by Taq DNA polymerase. Furthermore, two EcoR I sites were added to the construct for identification of recombinant plasmids using a single restriction enzyme. Taken together, the more efficient cloning performance and the lower cost of this vector as compared to the commercial T vector, suggests that it may be one of the best T vectors for cloning of PCR products.