Multiple activating chromatin modifications contribute to the function and relative strength of replication origins, suggesting that the chromatin environment does not regulate origins of replication as a simple binary switch, but rather acts as a tunable rheostat to regulate replication initiation events.
This strategy involves multiple and hierarchical chromatin modifications that regulate nuclear dynamics in response to a developmentally programmed signal(s), presumably of paracrine origin, before the resumption of meiosis.
Clearly, the function of transcription factors, as well as the predictive power with respect to transcriptional activation or repression, will require the combination of profiles for multiple factors and chromatin modifications to be fully understood.
Hattangadi, S. M., Wong, P., Zhang, L., Flygare, J. & Lodish, H. F. From stem cell to red cell: regulation of erythropoiesis at multiple levels by multiple proteins, RNAs, and chromatin modifications.
Only one PfEMP1 is expressed at the time and expression involves multiple layers of control involving chromatin modifications, nuclear positioning, and promoter-intron interactions [2], [42], [43].
The epigenetic signature of ES cells is characterized by coexistence of both activating and silencing chromatin modifications at multiple loci.
Together, these studies should provide an integrated view on the function and interplay of the multiple chromatin-remodeling complexes and other chromatin modifications that aid repair efficiency.
Activators work in large part by increasing PIC formation but can also act through other mechanisms, such as accelerating the rate of transcriptional elongation, promoting multiple rounds of transcription and directing chromatin modifications (reviewed in Green, 2005; Fuda et al., 2009; Weake and Workman, 2010).
Indeed, a striking number of chromatin regulators contain multiple modification recognition domains and many chromatin regulatory protein complexes contain multiple subunits that can potentially recognize different chromatin modifications [ 97].
