sentence: For instance , eRF1 – 1 mRNA levels were elevated in xrn4ski2 compared with xrn4 and WT ( 48 ) , supporting the involvement of both 5 ′ to 3 ′ and 3 ′ to 5 ′ cytoplasmic exoribonucleolytic pathways for turnover of fragments produced by cleavage of eRF1 – 1 mRNAs .