Intranuclear targeting of AML/CBFalpha regulatory factors to nuclear matrix-associated transcriptional domains
Department of Cell Biology
Medical Subject Headings
Cell Compartmentation; Core Binding Factor Alpha 2 Subunit; *DNA-Binding Proteins; Hela Cells; Humans; Microscopy, Fluorescence; Nuclear Matrix; *Proto-Oncogene Proteins; RNA Polymerase II; Trans-Activation (Genetics); Transcription Factors; *Transcription, Genetic; Transfection
Cell Biology | Life Sciences | Medicine and Health Sciences
The AML/CBFalpha runt transcription factors are key regulators of hematopoietic and bone tissue-specific gene expression. These factors contain a 31-amino acid nuclear matrix targeting signal that supports association with the nuclear matrix. We determined that the AML/CBFalpha factors must bind to the nuclear matrix to exert control of transcription. Fusing the nuclear matrix targeting signal to the GAL4 DNA binding domain transactivates a genomically integrated GAL4 responsive reporter gene. These data suggest that AML/CBFalpha must associate with the nuclear matrix to effect transcription. We used fluorescence labeling of epitope-tagged AML-1B (CBFA2) to show it colocalizes with a subset of hyperphosphorylated RNA polymerase II molecules concentrated in foci and linked to the nuclear matrix. This association of AML-1B with RNA polymerase II requires active transcription and a functional DNA binding domain. The nuclear matrix domains that contain AML-1B are distinct from SC35 RNA processing domains. Our results suggest two of the requirements for AML-dependent transcription initiation by RNA polymerase II are association of AML-1B with the nuclear matrix together with specific binding of AML to gene promoters.
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Citation: Proc Natl Acad Sci U S A. 1998 Feb 17;95(4):1585-9.