Structural features of hematopoiesis-specific RhoH/ARHH gene: high diversity of 5'-UTR in different hematopoietic lineages suggests a complex post-transcriptional regulation.
The hematopoiesis-specific RhoH gene is thought to be deregulated in B-cell non-Hodgkin's lymphoma (B-NHL), by either a chromosomal translocation or mutations, which affect its 5' regulatory region. The encoded Rho protein, always GTP-bound in vivo, was hypothesized to behave as a Rac antagonist. Extensive expression analysis allowed the detection of RhoH transcripts in all hematopoietic lineages (lymphoid, erythroid, myeloid), with a high level in lymphoid cells. To initiate investigations on the molecular mechanisms that regulate RhoH gene expression, Race-PCR and primer extension were conducted in the B-cell line Raji, which allowed (i) the establishment of RhoH complex intron/exon organization and (ii) the detection of several transcription initiation sites. In addition, a high 5' end heterogeneity of RhoH mRNAs was observed, due to alternative splicing of some 5' exons and to the use of these different transcription start sites. RT-PCR analysis led to the identification of this 5' end heterogeneity in different hematopoietic lineages. Discrepancies were particularly observed between B and T cells, due to an alternative splicing of one 5' exon (1b), which might be an important element in RhoH gene regulation. Such specific features have never been described for any Rho family member gene. They provide a molecular basis to study complex mechanisms involved in the control of RhoH expression.
Lahousse
Sébastien
S
U. 524 Inserm, Institut de Recherches sur le Cancer de Lille, Place de Verdun, 59045 Lille cedex, France.
Smorowski
Anne-Lise
AL
Denis
Claude
C
Lantoine
Danièle
D
Kerckaert
Jean-Pierre
JP
Galiègue-Zouitina
Sylvie
S
D020121:5' Untranslated Regions / Q000235:genetics*; D001402:B-Lymphocytes; D001483:Base Sequence; D002460:Cell Line; D045744:Cell Line, Tumor; D017931:DNA Primers; D005091:Exons / Q000235:genetics; D005786:Gene Expression Regulation / Q000235:genetics*; D018922:HL-60 Cells; D006410:Hematopoiesis / Q000235:genetics*; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D006801:Humans; D007438:Introns / Q000235:genetics; D020014:K562 Cells; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013601:T-Lymphocytes; D014157:Transcription Factors / Q000235:genetics*; D020298:U937 Cells; D020741:rho GTP-Binding Proteins / Q000235:genetics*
D020121:5' Untranslated Regions; D017931:DNA Primers; C447841:RhoH protein, human; D014157:Transcription Factors; D020741:rho GTP-Binding Proteins