In order to fully understand hwo the HIF-1 pathway is triggered, an understanding of how blmp-1 works is required. It was found that there is an effect of local histone modification when the round worms are exposed to hypoxic conditions. The histone (H3) is acetylated. This process unwinds the chromatin, giving increased chromatin accessibly. This means that more of the chromatin is able to be transcribed. Figure 5 (in the paper), demonstrates that blmp-1 receives a message that controls the acetylation. The figure further demonstrates (Figure 5C, as seen to the right) that the histone is acetylated twice as much in hypoxic conditions in comparison to normoxia, with the wild type round worms. In the blmp-1 mutants, however, there is not a similar increase in histone acetylation (Figure 5D, as seen to the right). Therefore, without blmp-1 there is not a trigger to open up the chromatin.

Figure 5: This is taken directly from Padmenhaba et al (2015). The image displays the effect of the blmp-1 transcription factor on the histone acetylation at the F45D3.4 promoter.