Subnucleäre Lokalisation des Transkriptionsfaktors STAT3

The transcription factor STAT3 is involved in a variety of biological functions. It is most essential for the signal transduction of interleukin-6 (IL-6) and related cytokines. In response to IL-6 stimulation STAT3 monomers are recruited by the gp130 subunit of the IL-6 receptor, become phosphorylated, dissociate, dimerize, and translocate into the nucleus where they bind to enhancer sequences of target genes. * The subnuclear localization of the transcription factor STAT3 was analyzed by confocal laserscanning microscopy. Activated STAT3 was found in dot-like structures within the nucleus which were termed STAT3 nuclear bodies. * The fusion protein STAT3-YFP was generated to visualize the nuclear translocation after stimulation in living cells. The formation of STAT3 nuclear bodies appeared to be transient. It correlated with STAT3 tyrosine phosphorylation kinetics. Indirect immunofluorescence revealed that STAT3 in nuclear bodies is phosphorylated on tyrosine 705 and serine 727. * FRAP- and FLIP-techniques allowed to analyse the mobility of STAT3-YFP in nuclear bodies. FRAP revealed that irreversibly bleached STAT3-YFP in nuclear bodies is substituted by unbleached STAT3-YFP. Moreover, a quantitative approach showed that STAT3 nuclear bodies consist of a mobile and an immobile fraction of STAT3. Taken together, on the one hand there is a rapid exchange of STAT3 in nuclear bodies with the environment and on the other hand the immobile STAT3 molecules are bound to an interaction partner. Nuclear STAT3 that was not accumulated in nuclear bodies diffuses freely in the nucleoplasm. * Furthermore, colocalization studies were performed with respect to the spatial relationship of STAT3 nuclear bodies and nuclear architecture. These studies showed that STAT3 nuclear bodies were neither colocalized with splicing factor compartments (SFC, "speckles") nor with PML bodies. STAT3 nuclear bodies appeared to be an autonomous subnuclear compartment. Interestingly, STAT3 nuclear bodies are colocalized with markers of transcriptionally active chromatin (i.e. acetylated histones, histone-acetyl-transferases). STAT3 nuclear bodies and nascent pre-mRNA are spatially accompanied. * For additional studies a deletion mutant called STAT3-?TAD709-YFP was generated. This mutant lacks the C-terminal transactivation domain (TAD). STAT3-TAD709-YFP showed a weak nuclear translocation after stimulation. STAT3-TAD709-YFP did not appear in nuclear bodies and it inhibited the formation of STAT3-wild type-nuclear bodies in a dominant-negative manner. This is a hint, that the transactivation domain of STAT3 could have a mediating function in the assembly of STAT3 nuclear bodies. One could imagine two functions of STAT3 nuclear bodies. (1) STAT3 nuclear bodies could be directly involved in active gene transcription. In this case STAT3 in nuclear bodies would be bound to DNA and is accompanied with transcriptional cofactors. (2) STAT3 nuclear bodies could serve as reservoirs for activated STAT3. Activated STAT3 could be recruited from these reservoirs to bind enhancer sequences of target genes.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2004

Author dc:creator

• Herrmann, Andreas

Contributors dc:contributor

• Heinrich, Peter C.

• info:eu-repo/classification/ddc/570
• Laser-Rastermikroskopie
• STAT
• Zellkern
• STAT3
• confocal laserscanning microscopy
• nuclear bodies
• Biowissenschaften, Biologie

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123630%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:62032