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L Steinmüller

Publications and source records attributed to L Steinmüller.

4 recordsLinked to original sources
PubMed2001

Regulation and composition of activator protein 1 (AP-1) transcription factors controlling collagenase and c-Jun promoter activities.

The activator protein 1 (AP-1) transcription factor is composed of heterodimers of the Fos/activating transcription factor (ATF) and Jun subfamilies of basic-region leucine-zipper (B-ZIP) proteins. In order to determine the identities of individual B-ZIP proteins in various AP-1 complexes we tested the effect of dominant-negative mutants to the B-ZIP proteins c-Fos, ATF2, ATF4 and CCAAT-enhancer-binding protein (C/EBP) on the activities of the collagenase and c-Jun promoters. These dominant-negative mutants inhibit DNA binding of wild-type B-ZIP proteins in a leucine-zipper-dependent fashion. Transcription of a collagenase promoter/reporter gene was induced in HepG2 hepatoma cells by expression of c-Fos and c-Jun, administration of PMA ("TPA") or by expression of a truncated form of MEK (mitogen-activated/extracellular-signal-regulated kinase kinase) kinase-1, MEKK1Delta. In all cases, the dominant-negative mutants A-Fos and A-ATF2 decreased collagenase promoter activity. However, A-ATF4 and A-C/EBP had no effect. A-Fos and A-ATF2 also reduced MEKK1Delta-induced stimulation of the c-Jun promoter. In contrast, constitutive c-Jun promoter activity was blocked solely by A-ATF2, strongly suggesting that ATF2 and/or an ATF2-dimerizing protein are of major importance for c-Jun transcription in unstimulated cells. These results demonstrate that AP-1 transcription factors of different compositions control c-jun gene transcription in resting or stimulated cells.

Amino Acid Sequence↗
PubMed2001

Modular structure of cAMP response element binding protein 2 (CREB2).

The transcription factor cAMP-response element binding protein 2 (CREB2), a member of the family of basic region leucine zipper proteins, has been suggested to function in the brain as a repressor of long-term memory. Using recombinant proteins we show that CREB2 binds in vitro to the palindromic cAMP response element derived from the secretogranin II gene. Recent studies of the chromogranin B, secretogranin II and enkephalin genes showed that CREB2 functioned as a repressor of cAMP-induced transcription. We analyzed the ability of CREB2 to repress transcription using model promoters. A molecular dissection of the CREB2 molecule revealed that CREB2 lacks a transferable repressor domain suggesting that CREB2 may function solely as a "passive" transcriptional repressor. In contrast, "active" repressor domains derived from the thyroid hormone receptor alpha or the NK10 zinc finger protein containing a "Krüppel associated box" could be transfered to a heterologous DNA-binding domain and functioned as fusion proteins in repressing transcription of a reporter gene. In addition, a strong activation domain located at the N-terminus was identified in the CREB2 protein suggesting that CREB2 may act as an activator of transcription by binding to different genetic regulatory elements.

Activating Transcription Factor 4↗
PubMed1989

[Stress fracture of the femoral neck in a marathon runner. Case report and review of the literature].

Stress fracture of the femoral neck is rare, and the conditions in which it occurs are complex. An unusually high, rhythmically acting force resulting from body weight and muscle tension leads to decompensation of the dynamic equilibrium otherwise prevalent in bone metabolism in conditions of adaptation. Even small differences in leg length predispose to fracture of the longer leg, owing to the increased muscular activity. Bone scanning is helpful in diagnosis when no signs of fracture are revealed by conventional radiography. Internal fixation that will allow weight-bearing should be attempted. In this case report an instance of this type of fracture in a marathon runner is presented.

Athletic Injuries↗