The apparent 'default expression' patterned by the MES-4/PRC2 antagonism is interesting, as both H3K36me areH3K27me are not noticeably affected by the observed reprogramming mechanisms, described below, that are active in Z2/Z3, even though multiple modifications that correlate with gene activation are significantly reduced.
We suggest that despite the successful application of ETD for sequencing of several peptides with multiple modifications, the N-terminus of H3 in the primary human adipocytes is so heavily and differentially modified that its heterogeneous products did not pass the MS/MS quality criteria used for identification in this study.
Mean ratios were also calculated for the peptides identified with multiple modifications as light and/or heavy forms.
As a consequence, two thirds of the phosphorylated sites in the learning set originate from proteins with multiple modifications.
While the utility of photoactive Protein Z has been previously demonstrated, it is very challenging to produce such a recombinant protein with multiple modifications.
Despite the advantages described above, broader adoption of this approach can be hampered by the difficulty of producing Protein Z with multiple modifications.
With the slow growth rate of Synechocystis PCC6803, each separate modification can be time consuming to generate with multiple modifications requiring many rounds of cloning, transformation, segregation and selection especially if marker-less clones are required.
Hence, a small number of hsdM genes can support a large number of hsdS genes to generate a system in which multiple modification enzymes with differing DNA sequence specificities are active simultaneously.
The carbamylation method could be combined with other proteases, like LysC, to ensure multiple modifications of each peptide.
Multiple modifications generally resulted in higher activities.
