Involved in the regulation of heterochromatin assembly at telomeric regions. Involved in the control of telomere length. Regulates spliceosome assembly by associating with brr2. Regulates the proper splicing of mRNAs of the shelterin components rap1 and poz1 to control telomeric heterochromatin assembly and telomere length. Interacts with brr2. Belongs to the TLS1 family. Extended N-terminus.