Transcription Factor Pit-1 Affects Transcriptional Timing in the Dual-Promoter Human Prolactin Gene

Abstract

Gene transcription occurs in short bursts interspersed with silent periods, and these kinetics can be altered by promoter structure. The effect of alternate promoter architecture on transcription bursting is not known. We studied the human prolactin (hPRL) gene that contains two promoters, a pituitary-specific promoter that requires the transcription factor Pit-1, and displays dramatic transcriptional bursting activity, and an alternate upstream promoter that is active in non-pituitary tissues. We studied large hPRL genomic fragments with luciferase reporters, and used bacterial artificial chromosome (BAC) recombineering to manipulate critical promoter regions. Stochastic switch mathematical modelling of single-cell time-lapse luminescence image data revealed that the Pit-1-dependent promoter showed longer, higher-amplitude transcriptional bursts. Knockdown studies confirmed that the presence of Pit-1 stabilised and prolonged periods of active transcription. Pit-1 therefore plays an active role in establishing the timing of transcription cycles, in addition to its cell-specific functions.

Current Insights in Prolactin Signaling and Ovulatory Function

“…In humans, a single 10 kb gene encoding PRL is located on chromosome six and contains five exons and four introns [51]. The PRL gene transcription process is regulated by two independent promoter regions: the proximal region that controls pituitary-specific expression and the more upstream 5000-bp region that directs extrapituitary expression of PRL [52]. Preprolactin, which is a protein 2-3 kDa heavier than mature PRL, represents the initial product of PRL mRNA translation, from which PRL is produced after removal of the 28-amino acid signal peptide by proteolytic cleavage [6,8].…”

“…However, due to the fact that it is usually composed of a PRL monomer and an IgG molecule that has a prolonged clearance rate similar to that of immunoglobulins, macroprolactin is characterized by limited bioavailability (as confined to the vascular system) and much lower bioactivity than PRL. Therefore, the predominance of macroprolactin, which is the main molecular form of PRL in the serum of patients with a normal concentration of monomeric PRL, is associated with no symptoms or a mild course of hyperprolactinemia [52,55,229,286].…”

Etiopathogenetic features of hyperprolactinemia in childhood

“…Проксимальна ділянка промотора (5000 bp) відповідає за гіпофізарну специфічну експресію, тоді як промоторна ділянка, що знаходиться на протязі вище, відповідає за екстрагіпофізарну експресію. кДНК пролактину людини має довжину 914 нуклеотидів і містить відкриту рамку зчитування з 681 нуклеотиду та кодує прогормон пролактин із 227 амінокислот [24].…”

Recent Findings on Hyperprolactinemia and its Pathological Implications: A Literature Review

“…Two promoter regions, which are independent of each other, are responsible for the PRL gene transcription. One of them is proximal or downstream which is responsible for the direction of pituitary-specific expression and the other is distal or upstream and directs the extrapituitary expression 5…”

“…One of them is proximal or downstream which is responsible for the direction of pituitary-specific expression and the other is distal or upstream and directs the extrapituitary expression. 5 In humans, the principal PRL-related symptoms, such as hypogonadism and infertility, result from the hypersecretion of this hormone, and its low level is not a common complication and has no specific side effects. 6 This may be due to the production of PRL outside the pituitary gland and probably pituitary hyperprolactinemia.…”