High impact information on FHL1

• We show that regulation of RP gene transcription via TOR and PKA in yeast involves the Forkhead-like transcription factor FHL1 and the two cofactors IFH1 (a coactivator) and CRF1 (a corepressor) [1].
• TOR regulates ribosomal protein gene expression via PKA and the Forkhead transcription factor FHL1 [1].
• In turn, Sfp1 influences the nuclear localization of Fhl1 and Ifh1, which bind to RP gene promoters [2].
• Loss of functional Fhl1p leads to cells that have only 20% the normal amount of RNA and that synthesize ribosomes at only 5-10% the normal rate [3].
• In vitro transcription of a UAS(RAP1) enhancer-driven reporter gene requires both Rap1p and TFIID and is independent of the Fhl1p-Ifh1p coregulator [4].

Biological context of FHL1

• Conversely, its overexpression by increased gene dosage partially compensates for the genetic inactivation of Fhl1p [5].
• Carboxy-terminal deletions removing the last third of the protein lead to a leaky growth phenotype with impaired rRNA maturation, as in the case of the fhl1 deletion [5].
• IFH1 (located on chromosome IV) was isolated as a dosage-dependent suppressor partially correcting the growth defect of the fhl1 deletion [5].
• One of these upstream activation sequence elements has an ATGTACGGATGT motif, which has previously been described as a putative binding site for the forkhead-like transcription factor Fhl1p [6].
• Two other genes, FHL1 and PEP5, are involved in the control of ribosome formation and vacuole biogenesis, respectively; and five genes, presently having unknown functions, could be new potentially interesting candidates for further studies in relation to yeast replicative aging [7].

Associations of FHL1 with chemical compounds

• Deletion of FHL1 reduces CPC2 transcription significantly in presence of glucose, but has no effect when the non-fermentable carbon source ethanol is provided [6].
• Increased amounts of the Fhl1p co-regulator Ifh1p induce CPC2 transcription even when ethanol is utilized [6].

Physical interactions of FHL1

• Surprisingly, loss of Hmo1 abolishes binding of Fhl1 and Ifh1 to RP promoters but does not significantly affect the level of transcriptional activity [8].

Other interactions of FHL1

• Hmo1 binding to RP promoters requires Rap1 and (to a lesser extent) Fhl1, proteins that also associate with RP promoters [8].
• Occasionally, multiseptate cells were also produced, indicating the involvement of fhl1 and fkh2 in efficient septum cleavage [9].

References