Abstract
Glycophorin C (GPC) is an integral membrane protein of human erythrocytes which plays an important role in regulating the deformability and mechanical stability of red cells. Recently, the structural gene for this glycoprotein has been cloned (Colin, Y., Le Van Kim, C., Tsapis, A., Clerget, M., d'Auriol, L., London, J., Galibert, F., and Cartron, J. P. (1989) J. Biol. Chem. 264, 3773-3780), and we have now determined the sequence of the 1050 base pairs of DNA preceding the transcription initiation site mapped in erythroid cells. This region contains different potential regulatory cis-acting elements found in a variety of eukaryotic promoters (TATA box, CAAT box, Sp1-binding site) as well as sequences present in the promoter and enhancer regions of genes specific for the erythroid lineage (CACCC box and NF-E1-binding site). Northern blot analysis and immunological studies indicate that the GPC gene is expressed in a large number of cells and tissues. However, the level of transcription as well as the glycosylation of the mature GPC differ in erythroid and nonerythroid cells. Primer extension analysis and mapping of the 5' end GPC mRNA by the polymerase chain reaction indicate that different transcription sites are utilized for the expression of the GPC gene in erythroid and nonerythroid tissues and cell lines.
Highlights
Four main species of sialic acid-rich glycoproteins known as glycophorins A, B, C, and D have been characterized on humanerythrocytes
Theprimarystructure of GPChas been deducedfrom protein sequence and cDNA analysis [9, 10] and found to be not related to Glycophorin A (GPA) and GPB
The normaglene is organized in four exons over 13.5-kilobase pair DNA and containstwo internal direct repeated domainosf 3.4 kb which are likely to derive from a recent duplication [11].More recently, preliminarystudies of GPC expression innormaland leukemic hematopoietic tissues suggested thatthis glycoprotein, in contrast to GPA and GPmBa,y not be erythroid specific [14]
Summary
Open and hatched boxes refer to the untranslated and coding sequences of exon 1, respectively. The beginning of intron 1 (Znt 1 ) is represented by a hatched line. Lightface and bold capital letters refer to the untranslated and coding sequences of exon 1, respectively, and small characters refer to flanking sequences. Position +1 is taken as the A nucleotide of the erythroid transcription initiation site (il) and is indicated by a large arrow. The small arrows at positions -11 and -57 indicate the two additional transcription initiation sites (i2 and13)identified in nonerythroid cells (see Fig. 5).The potential cis-acting regulatory sequences listed in Table I are boxed in. The small arrows at positions -11 and -57 indicate the two additional transcription initiation sites (i2 and13)identified in nonerythroid cells (see Fig. 5).The potential cis-acting regulatory sequences listed in Table I are boxed in. bp, base pairs
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