Collagen I and the fibroblast: high protein expression requires a new paradigm of post-transcriptional, feedback regulation.

Background Scaling protein production seems like a simple perturbation of transcriptional control. However, when embryonic tendon fibroblasts have to produce >50% procollagen and secrete it from the cell 4 times faster than the average protein, this taxes the cellular machinery and requires a fresh look at how the pathway is controlled. Ascorbate, a reducing agent, can stimulate procollagen production 6-fold. Procollagen mRNA levels goes up 6-fold but requires 3 days for the cell to accomplish this task. Secretion rates, the last cellular step in the process, also goes up 6-fold but this occurs in <1 h. What regulatory scheme is consistent with these properties?