Characterization of the human CD5 endogenous retrovirus-E in B lymphocytes.
All T lymphocytes and some B lymphocytes express CD5. This coreceptor is encoded by one gene that consists of 11 exons. We have previously described a B cell-specific alternative exon 1, leading to the synthesis of a protein, devoid of leader peptide, and, therefore, retained in the cytoplasm. The novel exon 1 originates from a human endogenous retrovirus (HERV) at a time interval between the divergence of New World monkeys from Old World monkeys, and prior to the divergence of humans from Old World monkeys. Based on sequence similarity to gamma-retroviruses, it was categorized as class I: based on the specificity of its primer binding site, it was allotted to the subclass E, and based on its location within the cd5 gene, named HERV-E.CD5. Alternative transcripts were detected in lymphoid organs including fetal liver (not adult liver), more particularly in CD5-negative cell surface B-1b than in CD5-positive cell surface B-1a, and not at all in B-2 cells. By alignment of 5' long terminal repeats, HERV-E.CD5 was distinguished from similar proviruses. This could be central to the regulation of membrane expression of CD5 in human B lymphocytes, and, thereby, to the strength of the B-cell antigen receptor signaling.
Renaudineau
Y
Y
Laboratory of Immunology, Brest University Medical School, 2 avenue Foch, BP824, F-29609 Brest, France.
Vallet
S
S
Le Dantec
C
C
Hillion
S
S
Saraux
A
A
Youinou
P
P
D001402:B-Lymphocytes / Q000378:metabolism*; D018956:CD5 Antigens / Q000235:genetics* / Q000378:metabolism*; D020077:Endogenous Retroviruses / Q000145:classification* / Q000235:genetics*; D005091:Exons; D006801:Humans; D008957:Models, Genetic; D020079:Terminal Repeat Sequences
D018956:CD5 Antigens