Detection of an appropriate kinase activity in branchial arches I and II that coincides with peak expression of the Treacher Collins syndrome gene product, treacle

Treacher Collins syndrome (TCS) is an autosomal dominant craniofacial disor der involving the mid and lower face and, in particular, the tissues affect ed arise solely from embryonic branchial arches I and II. TCOF1, the gene i nvolved in TCS, has been cloned and although the function of the encoded pr otein, treacle, has not yet been established, it exhibits peak expression i n the branchial arches, Treacle contains a series of repeating units of aci dic and basic residues, which are predicted to contain putative casein kina se II (CKII) and protein kinase C (PKC) phosphorylation site motifs, In add ition, treacle has weak homology to two phosphorylation-dependent nucleolar proteins, which shuttle between the cytoplasm and nucleolus, Based on thes e observations, phosphorylation of treacle may be important for its functio n. In this study, GST-treacle fusion peptides were constructed using partic ular TCOF1 exons that contained potential CKII and PKC phosphorylation site s, These were used as substrates in in vitro kinase assays and showed that treacle fusion peptides can be phosphorylated by the appropriate kinases, F urthermore, using tissue extracts we have demonstrated that in avian embryo nic branchial arches I and II there is a kinase activity that can phosphory late treacle peptides that is consistent with CKII site recognition, This a ctivity coincides with the reported high expression of treacle in these tis sues at early developmental stages and declines later in development.