3 research outputs found
YY1 negatively regulates mouse myelin proteolipid protein (Plp1) gene expression in oligodendroglial cells
YY1 (Yin and Yang 1) is a multifunctional, ubiquitously expressed, zinc finger protein that can act as a transcriptional activator, repressor, or initiator element binding protein. Previous studies have shown that YY1 modulates the activity of reporter genes driven by the myelin PLP (proteolipid protein) (PLP1/Plp1) promoter. However, it is known that Plp1 intron 1 DNA contains regulatory elements that are required for the dramatic increase in gene activity, coincident with the active myelination period of CNS (central nervous system) development. The intron in mouse contains multiple prospective YY1 target sites including one within a positive regulatory module called the ASE (anti-silencer/enhancer) element. Results presented here demonstrate that YY1 has a negative effect on the activity of a Plp1-lacZ fusion gene [PLP(+)Z] in an immature oligodendroglial cell line (Oli-neu) that is mediated through sequences present in Plp1 intron 1 DNA. Yet YY1 does not bind to its alleged site in the ASE (even though the protein is capable of recognizing a target site in the promoter), indicating that the down-regulation of PLP(+)Z activity by YY1 in Oli-neu cells does not occur through a direct interaction of YY1 with the ASE sequence. Previous studies with Yy1 conditional knockout mice have demonstrated that YY1 is essential for the differentiation of oligodendrocyte progenitors. Nevertheless, the current study suggests that YY1 functions as a repressor (not an activator) of Plp1 gene expression in immature oligodendrocytes. Perhaps YY1 functions to keep the levels of PLP in check in immature cells before vast quantities of the protein are needed in mature myelinating oligodendrocytes
Adenylation and <i>S</i>‑Methylation of Cysteine by the Bifunctional Enzyme TioN in Thiocoraline Biosynthesis
The antitumor agent thiocoraline
is a nonribosomally biosynthesized
bisintercalator natural product, which contains in its peptidic backbone
two <i>S</i>-methylated l-cysteine residues. <i>S</i>-Methylation occurs very rarely in nature, and is observed
extremely rarely in nonribosomal peptide scaffolds. We have proposed
that during thiocoraline biosynthesis, TioN, a stand-alone adenylation
domain interrupted by the <i>S</i>-adenosyl-l-methionine
binding region of a methyltransferase enzyme, is capable of performing
two functions: the adenylation and <i>S</i>-methylation
of l-cysteine. Herein, by preparation of knockouts of TioN
and its MbtH-like protein partner TioT, we confirmed their role in
thiocoraline biosynthesis. We also co-expressed recombinant TioN and
TioT and biochemically investigated three potential pathways involving
activation, methylation, and loading of l-cysteine onto the
TioN partner thiolation domain, TioS(T<sub>4</sub>). The valuable
insights gained into the pathway(s) followed for the production of <i>S</i>-Me-l-Cys-<i>S</i>-TioS(T<sub>4</sub>) will serve as a guide for the development of novel engineered interrupted
adenylation enzymes for combinatorial biosynthesis