Ribosomal protein S19 expression during erythroid differentiation

Abstract

The gene encoding ribosomal protein S19 (RPS19) has been shown to be mutated in 25% of the patients affected by DiamondBlackfan anemia (DBA), a congenital erythroblastopenia. As the role of RPS19 in erythropoiesis is still to be defined, we performed studies on RPS19 expression during terminal erythroid differentiation. Comparative analysis of the genomic sequences of human and mouse RPS19 genes enabled the identification of 4 conserved sequence elements in the 5 region. Characterization of transcriptional elements allowed the identification of the promoter in the human RPS19 gene and the localization of a strong regulatory element in the third conserved sequence element. By Northern blot and Western blot analyses of murine splenic erythroblasts infected with the anemia-inducing strain Friend virus (FAV cells), RPS19 mRNA and protein expression were shown to decrease during terminal erythroid differentiation. We anticipate that these findings will contribute to further development of our understanding of the contribution of RPS19 to erythropoiesis. IntroductionThe mammalian ribosome is composed of 4 RNA species and 80 different ribosomal proteins. [1][2][3][4][5] One of these proteins, the ribosomal protein S19 (RPS19) is localized at the beak of the small ribosomal subunit 40S 6 and mutations in the gene encoding RPS19 have been identified in 25% of the patients affected by Diamond-Blackfan anemia (DBA), a rare congenital erythroblastopenia. 7,8 However, the mechanistic understanding of the relation between RPS19 and erythropoiesis and, specifically, the impact of RPS19 mutations in DBA remains to be defined.At the transcriptional level, all ribosomal protein genes must be coordinated to allow for efficient and balanced protein synthesis. Although mammalian ribosomal protein genes are not clustered 9 but rather dispersed throughout the genome, 2 they are transcribed at very similar rates due to the equivalent strength of their promoters. 10 Such coordinated activity of the promoters of these numerous ribosomal protein genes is regulated transcriptionally through the binding of transcription factors to specific promoter sequence elements. 11 The cis-acting transcriptional regulatory elements and the trans-acting factors, which bind to these elements, have been characterized in the region located upstream of the translation initiation codon, in a few human 12,13 and mouse ribosomal protein genes. 10,11,[14][15][16][17][18][19][20][21][22][23][24][25] However, transcriptional control of most of these genes, including the RPS19 gene, remains to be defined.In the present study, we provide information on the transcriptional regulatory elements in the 5Ј region upstream of the translation initiation codon in the human RPS19 gene. Alignment of the human and mouse genomic sequences from this region allowed us to delineate 4 consensus regions present in both sequences. The Neural Network Promoter Prediction software (LBNL, Berkeley, CA) 14-16 identified a human RPS19 gene promoter, which was confirmed to have promoter a...

Apoptotic mechanisms in the control of erythropoiesis

“…174 There is clear evidence that the mutation of this gene is responsible for the development of erythroblastopenia in DBA patients. 175 However, it remains largely unclear why the loss of this ribosomal protein, whose synthesis is observed particularly in immature erythroblasts and decreasing progressively during erythroid maturation, 176 induces the development of anemia and to the increased sensitivity to apoptosis observed in DBA patients.…”

Protein localization in disease and therapy

“…In contrast with the previously described examples, mutations that disrupt the zinc finger domain of the transcription factor autoimmune regulator (AIRE), which are present in patients with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy, have been reported to cause cytoplasmic retention despite an intact nuclear targeting signal (Bjorses et al, 2000). Mutations within the nucleolar localization signal (NoS) of the ribosomal protein S19 (RPS19) have also been reported to be involved in disease development: in patients with Diamond-Blackfan anemia these mutations prevent the correct targeting of RPS19 to the nucleoli (Da Costa et al, 2003a). The major components of the eukaryotic cell are the cytosol, the nucleus, the nucleolus, the endoplasmic reticulum (ER), the Golgi complex, mitochondria and the peroxisome.…”

Diamond-Blackfan anemia: erythropoiesis lost in translation

“…Seemingly in conflict with these data, RPS19 expression levels are high in primitive cells and progressively decrease in more mature cells such as erythroblasts. 23,26,27 In addition, there may be a proliferative defect in more primitive hematopoietic progenitors because CD34 ϩ CD38 Ϫ multipotent progenitor cells from patients with RPS19-deficient DBA show a decreased proliferation rate in vitro, which can be corrected by RPS19 gene transfer. 26…”