ABSTRACT
We describe a pathway by which the master transcription factor PU.1 regulates human monocyte/macrophage differentiation. This includes miR-424 and the transcriptional factor NFI-A. We show that PU.1 and these two components are interlinked in a finely tuned temporal and regulatory circuitry: PU.1 activates the transcription of miR-424, and this up-regulation is involved in stimulating monocyte differentiation through miR-424-dependent translational repression of NFI-A. In turn, the decrease in NFI-A levels is important for the activation of differentiation-specific genes such as M-CSFr. In line with these data, both RNAi against NFI-A and ectopic expression of miR-424 in precursor cells enhance monocytic differentiation, whereas the ectopic expression of NFI-A has an opposite effect. The interplay among these three components was demonstrated in myeloid cell lines as well as in human CD34+ differentiation. These data point to the important role of miR-424 and NFI-A in controlling the monocyte/macrophage differentiation program.
Subject(s)
Cell Differentiation , Hematopoiesis , Macrophages/cytology , Macrophages/metabolism , MicroRNAs/genetics , Monocytes/cytology , Monocytes/metabolism , Proto-Oncogene Proteins/metabolism , Trans-Activators/metabolism , Base Sequence , Cells, Cultured , Humans , NFI Transcription Factors/genetics , NFI Transcription Factors/metabolism , Protein Binding , Up-RegulationABSTRACT
The discovery of microRNAS (miRNAs) and of their mechanism of action has provided some very new clues on how gene expression is regulated. These studies established new concepts on how posttranscriptional control can fine-tune gene expression during differentiation and allowed the identification of new regulatory circuitries as well as factors involved therein. Because of the wealth of information available about the transcriptional and cellular networks involved in hematopoietic differentiation, the hematopoietic system is ideal for studying cell lineage specification. An interesting interplay between miRNAs and lineage-specific transcriptional factors has been found, and this can help us to understand how terminal differentiation is accomplished.
Subject(s)
Hematopoiesis/genetics , Hematopoiesis/physiology , MicroRNAs/genetics , MicroRNAs/metabolism , Cell Differentiation/genetics , Cell Differentiation/physiology , Gene Expression Regulation, Developmental , Humans , Leukemia/genetics , Leukemia/metabolism , Models, Biological , RNA, Neoplasm/genetics , RNA, Neoplasm/metabolism , Transcription Factors/metabolismABSTRACT
Small nucleolar RNAs (snoRNAs) were utilized to express Rev-binding sequences inside the nucleolus and to test whether they are substrates for Rev binding and transport. We show that U16 snoRNA containing the minimal binding site for Rev stably accumulates inside the nucleolus maintaining the interaction with the basic C/D snoRNA-specific factors. Upon Rev expression, the chimeric RNA is exported to the cytoplasm, where it remains bound to Rev in a particle devoid of snoRNP-specific factors. These data indicate that Rev can elicit the functions of RNA binding and transport inside the nucleolus.
