Abstract
Interferon consensus sequence–binding protein (Icsbp) is required for terminating emergency granulopoiesis, an episodic event responsible for granulocyte production in response to infections and a key component of the innate immune response. Icsbp inhibits the expression of Stat3 and C/ebpβ, transcription factors essential for initiating and sustaining granulopoiesis, and activates transcription of Fanconi C (FANCC), a DNA repair protein. In prior studies, we noted accelerated bone marrow failure in Fancc−/− mice undergoing multiple episodes of emergency granulopoiesis, associated with apoptosis of bone marrow cells with unrepaired DNA damage. Additionally, we found increased expression of Fanconi C and F proteins during emergency granulopoiesis. These findings suggest that Icsbp protects the bone marrow from DNA damage by increasing activity of the Fanconi DNA repair pathway, but the mechanisms for FANCC activation during initiation of emergency granulopoiesis are unclear. In this study, we observed that Stat3 and C/ebpβ activate FANCC transcription and contribute to DNA repair. Our findings indicate that FancC expression is increased during Stat3- and C/ebpβ-induced initiation of emergency granulopoiesis by these transcription factors and is maintained through termination by Icsbp. Our work reveals that Stat3- and C/ebpβ-mediated FancC expression is a critical component for initiating and sustaining key innate immune responses.
Highlights
Interferon consensus sequence– binding protein (Icsbp) is required for terminating emergency granulopoiesis, an episodic event responsible for granulocyte production in response to infections and a key component of the innate immune response
Because Stat3 and C/ebp are required to initiate and sustain emergency granulopoiesis, we considered the possibility that these transcription factors activate the Fanconi C (FANCC) promoter early in this process
We found Stat3 and C/ebp, essential transcription factors for initiating and sustaining emergency granulopoiesis, are involved in protecting the genome by increasing the expression of Fanconi C
Summary
We identified an Icsbp binding cis element in the proximal FANCC promoter (Ϫ48 to Ϫ56 bp) [9]. We investigated possible additive or cooperative effects of these transcription factors on the FANCC promoter despite interacting with discrete binding sites For these studies, we co-transfected U937 cells with the 1.0 FANCC promoter/firefly luciferase reporter vector and various combinations of vectors to overexpress Stat, C/ebp-Lap, or Icsbp. Overexpression of Icsbp, Stat, or C/ebp significantly increased the reporter activity of the MMC-treated plasmid in IL1 transfectants (p Ͻ 0.001, n ϭ 6) but had no effect on the activity of reporter vectors that had not been MMC-treated (Fig. 6A). We found that knockdown of FancC prevented Icsbp, Stat, or C/ebp overexpression from rescuing the reporter activity of the MMC-treated plasmid (Fig. 4A) These results suggested that these transcription factors were acting through a FancCdependent mechanism to drive DNA cross-link repair
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have