Characterization of the expression and gene promoter of CD22 in murine B cells.
CD22 is a B cell-restricted surface molecule which may play an important role in interactions between B cells and other cells and in regulating signals through the B cell receptor (BCR) complex. Here we have examined whether the mouse is a suitable in vivo model for studying CD22 functions. In primary and secondary lymphoid organs of adult mice CD22 is on all mature B cells, including resting IgM+IgD+ B cells, IgG+ HSA(lo) memory B cells, syndecan+ plasma cells and CD5+ B cells, but it is not on immature IgM+IgD- B cells. Biochemical analysis revealed that murine CD22 is associated with the IgM receptor in some, but not all, CD22+ B leukemic and lymphoma cell lines; as with human CD22, murine CD22 is rapidly phosphorylated on tyrosine after ligation of the BCR. In the CD22- murine pro-B cell line, FEMCL, CD22 expression was inducible by treatment with phorbol 12-myristate 13-acetate. A genomic fragment of the cd22b allele containing 1.3 kb 5' of exon 1 was sequenced in order to identify potential DNA regulatory elements in the CD22 promoter region. Consensus sequences for transcription factor binding sites including PU.1, AP-1, AP-2, C/EBP and SP-1 were present, but no classical TATA elements or initiator motifs were evident at relevant positions. The 1.3-kb promoter fragment 5' of exon 1 was sufficient for directing basal promoter activity in B and T cells. There was no significant sequence similarity between the murine and human cd22 gene promoters, although both contain repetitive elements and Sp-1 and AP1 binding sites. Thus, murine CD22 shares a number of features with human CD22 and the mouse provides a suitable model system for elucidating the function of CD22 in vivo.
Andersson
K B
KB
Department of Microbiology, University of Washington, Seattle 98195-7242, USA.
Draves
K E
KE
Magaletti
D M
DM
Fujioka
S
S
Holmes
K L
KL
Law
C L
CL
Clark
E A
EA
D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics*; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D001483:Base Sequence; D015815:Cell Adhesion Molecules; D002460:Cell Line; D005091:Exons / Q000276:immunology; D037102:Lectins; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000276:immunology*; D012333:RNA, Messenger / Q000032:analysis; D051918:Sialic Acid Binding Ig-like Lectin 2; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; C497868:Cd22 protein, mouse; D015815:Cell Adhesion Molecules; D037102:Lectins; D012333:RNA, Messenger; D051918:Sialic Acid Binding Ig-like Lectin 2; D013755:Tetradecanoylphorbol Acetate