We investigated the role of microRNAs (miRNA) 17-5p, 20a and 106a in monocytic differentiation and maturation. In unilineage monocytic culture generated by haematopoietic progenitor cells these miRNAs are downregulated, whereas the transcription factor acute myeloid leukaemia-1 (AML1; also known as Runt-related transcription factor 1, Runx1) is upregulated at protein but not mRNA level. As miRNAs 17-5p, 20a and 106a bind the AML1 mRNA 3'UTR, their decline may unblock AML1 translation. Accordingly, transfection with miRNA 17-5p-20a-106a suppresses AML1 protein expression, leading to M-CSF receptor (M-CSFR) downregulation, enhanced blast proliferation and inhibition of monocytic differentiation and maturation. Treatment with anti-miRNA 17-5p, 20a and 106a causes opposite effects. Knockdown of AML1 or M-CSFR by short interfering RNA (siRNA) mimics the action of the miRNA 17-5p-20a-106a, confirming that these miRNAs target AML1, which promotes M-CSFR transcription. In addition, AML1 binds the miRNA 17-5p-92 and 106a-92 cluster promoters and transcriptionally inhibits the expression of miRNA 17-5p-20a-106a. These studies indicate that monocytopoiesis is controlled by a circuitry involving sequentially miRNA 17-5p-20a-106a, AML1 and M-CSFR, whereby miRNA 17-5p-20a-106a function as a master gene complex interlinked with AML1 in a mutual negative feedback loop.

Idiopathic retroperitoneal fibrosis (IRF) is a rare disease often causing obstructive uropathy. We evaluated the clinicopathologic features of 24 patients with IRF to characterize the histopathology of the disease and to provide a framework for the differential diagnosis with other retroperitoneal fibrosing conditions. Retroperitoneal specimens were analyzed by light and electron microscopy and by immunohistochemistry. Most patients presented with abdominal/lumbar pain, constitutional symptoms, and high acute-phase reactants. Overall, 20 had ureteral involvement and 13 developed acute renal failure. The retroperitoneal tissue consisted of a fibrous component and a chronic inflammatory infiltrate with the former characterized by myofibroblasts within a type-I collagen matrix. The infiltrate displayed perivascular and diffuse patterns containing lymphocytes, macrophages, plasma cells, and eosinophils. The perivascular aggregates had a central core of CD20(+) cells and a mantle of CD3(+) cells in equal proportions. In the areas of diffuse infiltrate, CD3(+) cells outnumbered the CD20(+) cells. Most plasma cells were positive for the IgG4 isotype. Small vessel vasculitis was found in the specimens of 11 patients. Our study indicates that a sclerotic background with myofibroblasts associated with a diffuse and perivascular infiltrate mainly consisting of T and B lymphocytes may be a pathological hallmark of IRF.

Many nuclear and nucleolar small RNAs are accumulated as nonpolyadenylated species and require 3-end processing for maturation. Here, we show that several genes coding for box C/D and H/ACA snoRNAs and for the U5 and U2 snRNAs contain sequences in their 3 portions which direct cleavage of primary transcripts without being polyadenylated. Genetic analysis of yeasts with mutations in different components of the pre-mRNA cleavage and polyadenylation machinery suggests that this mechanism of 3-end formation requires cleavage factor IA (CF IA) but not cleavage and polyadenylation factor activity. However, in vitro results indicate that other factors participate in the reaction besides CF IA. Sequence analysis of snoRNA genes indicated that they contain conserved motifs in their 3 noncoding regions, and mutational studies demonstrated their essential role in 3-end formation. We propose a model in which CF IA functions in cleavage and polyadenylation of pre-mRNAs and, in combination with a different set of factors, in 3-end formation of nonpolyadenylated polymerase II transcripts.snoRNAs belong to a complex family of RNA molecules localized in the nucleolus, where they participate in rRNA processing (35) and in the modification of several classes of RNA substrates: rRNAs (5,7,33,40,48,54), snRNAs (24,30,55), and possibly mRNAs (13,20). They work in combination with specific sets of proteins, forming ribonucleoprotein complexes; both the structure of the particles and their activity are highly conserved in evolution, as they are present and perform the same activity in archaebacteria and in eukaryotes (42). snoRNA coding units have quite a peculiar gene organization: the majority of metazoan and a few yeast snoRNAs are encoded in introns of protein-coding genes, while most yeast snoRNAs and a few vertebrate ones derive from independent transcription units, either monocistronic or polycistronic (59). Despite this heterogeneous organization, snoRNA biosynthesis relies on a common mechanism: entry sites for 5Ј-3Ј and 3Ј-5Ј exonucleases are produced from precursor molecules and allow the release of mature snoRNAs (2,43,44,56). In independently transcribed snoRNAs, such entry sites are often generated by the Rnt1p endonuclease (15, 16). In many cases, however, cleavage sites are absent in the 3Ј portion of the pre-snoRNAs, suggesting that processing starts from the 3Ј end of the primary transcript.Like genes coding for mRNAs, snoRNA genes are transcribed by RNA polymerase II. 3Ј-end formation of pre-mRNAs is accomplished by a two-step reaction, which involves endonucleolytic cleavage followed by addition of a poly(A) tail to the upstream cleavage product (60). The yeast cleavage and polyadenylation machinery consists of several complexes: for specific cleavage, cleavage factor IA (CF IA), CF IB, and CF II are required, while polyadenylation occurs when CF IA, CF IB, Pap1p, and polyadenylation factor I (PF I) are present (3,18,31,32,36,37). A complex containing PF I and CF II activity (named cleavage and polyadenylation facto...

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