DNA is not just shoved into the nucleus of a cell like a college boy’s clothes jammed into his closet (maybe that was just my husband?). The organization of the nucleus has been getting more attention lately, and the results are pretty fascinating. Today’s image is from a recent paper showing the association of a promoter to nuclear pores.
The organization of the nucleus may depend on the tethering of chromatin, or packaged DNA, to the nuclear envelope. While some past results have suggested that actively expressed regions of chromatin are associated with the nuclear envelope in some organisms, other results have shown localization of actively expressed genes at internal nuclear speckles in other organisms. A recent paper shows a link between the nuclear pore and a promoter, which is a region of DNA that initiates the expression of a nearby gene. Rohner and colleagues found that the heat shock promoter hsp-16.2 interacts with the nuclear pore after heat shock, a type of stress, in worms. Without heat shock, the promoter still maintained a perinuclear localization. Using super-resolution structured illumination microscopy (SR-SIM) to achieve 100-nm resolution, Rohner and colleagues found that after heat shock, the promoter’s localization to the nuclear pore complex increased. These results suggest that this stress-activated promoter may direct chromatin to the nuclear pores, where genes can be more easily accessed by transcription machinery. In the image above, a 200-cell stage worm embryo is stained to show the localization of the hsp-16.2 promoter (green) at the nuclear envelope (red, DNA is in blue) under normal circumstances.
BONUS!! Click here for a video of a 3D reconstruction of super-resolution images showing nuclear pores (green) and nuclear envelope (lamina, red).
Rohner, S., Kalck, V., Wang, X., Ikegami, K., Lieb, J., Gasser, S., & Meister, P. (2013). Promoter- and RNA polymerase II-dependent hsp-16 gene association with nuclear pores in Caenorhabditis elegans originally published in the Journal of Cell Biology, 200 (5), 589-604 DOI: 10.1083/jcb.201207024