Transcriptional repression of band 3 and CAII in v-erbA transformed erythroblasts accounts for an important part of the leukaemic phenotype.
The v-erbA oncogene confers two prominent properties on transformed erythroblasts: a block of spontaneous differentiation and tolerance to wide variations in the pH or ionic strength of culture medium. V-erbA acts as a constitutive repressor of erythrocyte-specific gene transcription, arresting the expression of at least three different erythroid genes: the erythrocyte anion transporter (band 3), carbonic anhydrase II (CAII) and delta-aminolevulinate synthase (ALA-S). To test whether or not the v-erbA induced repression of these genes is causally related to the v-erbA induced leukaemic phenotype, we have reintroduced the genes for band 3 or CAII into transformed erythroblasts via retrovirus vectors. We show here that such erythroblasts, expressing v-erbA, require the same narrow range of medium pH and ion concentration for growth as do transformed erythroblasts lacking v-erbA, i.e. the v-erbA induced tolerance to pH variation was abrogated. The v-erbA induced differentiation block, however, remained unaffected by the re-expression of band 3 and was only slightly affected by the re-expression of CAII. Our experiments show that the two v-erbA-related 'erythroblast transformation parameters' are separable: suppression of band 3 and CAII accounts for one parameter (pH/ion tolerance), while the second parameter (differentiation block) must involve v-erbA regulation of a different set of target genes.
Department of Molecular Biology, CMB, Karolinska Institute, Stockholm, Sweden.
S
S
Fuerstenberg
I
I
Leitner
C
C
Schroeder
H
H
Schwarz
B
B
Vennström
H
H
Beug
D000624:5-Aminolevulinate Synthetase / Q000235:genetics; D001355:Alpharetrovirus / Q000235:genetics; D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000235:genetics*; D027321:Anion Transport Proteins; D001483:Base Sequence; D002256:Carbonic Anhydrases / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics; D002454:Cell Differentiation; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D002472:Cell Transformation, Viral / Q000235:genetics; D002478:Cells, Cultured; D002642:Chick Embryo; D004900:Erythroblasts / Q000378:metabolism / Q000382:microbiology; D005347:Fibroblasts / Q000382:microbiology; D015972:Gene Expression Regulation, Neoplastic; D005822:Genetic Vectors; D006863:Hydrogen-Ion Concentration; D007942:Leukemia, Experimental / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D018774:Oncogene Proteins v-erbA; D010641:Phenotype; D015682:Retroviridae Proteins, Oncogenic / Q000235:genetics*
D001457:Anion Exchange Protein 1, Erythrocyte; D027321:Anion Transport Proteins; D002352:Carrier Proteins; D018774:Oncogene Proteins v-erbA; D015682:Retroviridae Proteins, Oncogenic; D000624:5-Aminolevulinate Synthetase; D002256:Carbonic Anhydrases