TLK1B mRNA is translationally upregulated by agents causing DSBs. A. incubation with doxorubicin causes a time-dependent increase in TLK1B expression without a change in the mRNA level. 2 × 106 cells were incubated with 0.2 μg/ml doxorubicin for increasing times, and then the proteins and RNA were separately extracted and processed for western and northern blots of TLK1B (left panel). Aliquots of 2 × 105 were labeled with 30 μCi of tran35S-label for the last 20 min of each time point (right panel). B. Redistribution of the TLK1B transcript in the polysomes of MM3MG cells expressing TLK1B. Cell extracts of control and irradiated cells (2×107) were prepared and sedimented for 2 h through sucrose gradients. Fraction aliquots were applied to a membrane in duplicates with a slot-blotter. The membrane was cut into strips and probed with either, an oligonucleotide specific for TLK1B, or with a cDNA for actin. Fractions corresponding to heavy polysomes (≥ 6 ribisomes), light (2–5 ribosomes), 80S, 60S and 40S ribosomal subunits, and small RNPs (Unbound) are indicated.